Doctor Who comes to mind, but not much else.

X-Files lost both Mulder and Scully at times, but got them back. I suspect it would not have survived otherwise.

Definitely true for Dr. Who and James Bond. Dr. Who, they basically made it part of the lore so it makes sense to help audiences accept that there will be a new actor given that the actor was ill. It was a lucky that the setting was sci-fi to help make it more accepting and is a rare successful case imo. Bond, its not exactly story driven (most recent one with Craig being an exception) and they have been able to leverage the role into a prestigious role for actors.

If I was the writer for the witcher, I would name the witcher starting from season 4 as "Witcher 2" or "Witcher: some subtitle" with Liam appearing as Geralt as a sort of reference to the fact that Geralt does appear different from game to game (have Yen comment you look different and Liam replies new game engine or new graphics). Could also have a body double shot body down of Geralt enter a barber shop for a haircut and come out as Liam as another reference to the fact that you can sometimes change your appearance in video games (including facial structure) by going to such a salon. Given that this is too humorous for a show like the Witcher and the writers mock the video games, I doubt it though.

Well, they did better about staying close to the books than the morons writing the Wheel of Time. That show was horrendous from the word "Go."

And Batman. Adam West was the third actor to play that role.

Also the 80s TV series Robin of Sherwood featured two actors for Robin.
When Michael Praed left the show, Robin of Locksley was killed and the hood was passed on to Jason Connery aka Robert of Huntington.
They used the existing lore here. The lore has two origin stories one of a lower class guy and one of a high noble.
While Robin of Locksley was no noble in this TV series, the second Robin was. Before his identity was uncovered, Robert would infiltrate the sheriff's castle, then put on his hood and act as Robin. He must have learned from Bruce Wayne.

There were loads of different actors playing Robin over the decades (same for many other famous chars like Sherlock Holmes).

But if we stick to contemporary ips, another movie / TV series with a couple of different actors would be the Jack Ryan series, starring Alec Baldwin, Harrison Ford, Ben Afleck, Chris Pine, John Krasinski.

I've played all the games (though not all of them were a full playthrough) and I'm actively reading the books, but I still love the show. In fact, the show convinced me to get the books. I loved the games but wasn't super invested in the characters, world or story until the show came out. Then, the show got me started on the books and now I love all of it. Even after I began reading the books, I still don't understand the hate for the show.

Adam West was in his own adaption of Batman, as was Bale and Keaton. If Witcher was rebooted with Liam, it makes sense to make this comparison.

Robin of Sherwood, I never saw but apparently the show ended with one series (Im guessing that is the equivalent of season in the US) after the change. I know that US and UK tv is very different with less focus on pumping multiple seasons out of an IP in the UK compared to the US but the series did end quickly after the actor change which is what is being discussed (or at least a decline in reception).

Regarding many different people playing Robin, Sherlock, or Jack Ryan; this is a completely different issue like Batman. These are different interpretations and depictions of the character created by different writers and showrunners. Being cast by a different actor is not only natural but expected to help distance from a previous depiction of a character. This is very different from the case in the Witcher or the other media I pointed out where the main lead actor is changed while the story and character itself is meant to remain the same depiction/character.

The opposite is true:
Connery actually played in 2 more episodes than Praed.
Season 1 (Praed): 5 episodes
Season 2 (Praed): 6 episodes
Season 3 (Connery): 13 episodes

The show was never meant to run for ages. I quote the producer "you can only infiltrate the castle so often, at some point they close all the secret entrances".
(My example originally was more about how the lore can suit an actor change, but it shows now, that a different actor can actually be good)

And yes, West had his own interpretation, but there were already TWO before him. The franchise didn't die when Batman #2 came to the stage. Talking about West ... how many Catwomen were there in the show?

I mentioned the Robins and Sherlocks to show that people are too fixated on actors. It's all roles adapted from books.
Now we see Witcher #3 coming to live. So what? Who complained that Cavill was not the original actor? He is not the first one holding the silver sword.

Jack Ryan however is NOT a different issue: All movies are based on the same book series and play in the same universe. And yes, I was also upset, that the role was taken from Baldwin and given to Ford.
But still ... they got 4 different actors before they even started a TV series with a fifth one. And it worked.

We also now have 3 different Dumbledoors (ok, one is way younger), works as well.

But we can argue up and down, back and forth. There will be a new actor playing that role and we have to come to terms with it and that's the end of the story really. Cavill had signed a limited contract and now returns to movies ... why not.
Changing an actor does not mean that everything is going downhills. It can happen, but nothing is set.

That rings true. He is a good actor and has a lot on his table. Why not focusing on other projects. He gave us a great performance. Thanks to him, hooefully we will keep watching him in other roles.

I guess Im mistaken in the never although I do think it is very very rare for a show to survive an actor, especially the main actor, from getting replaced in the story and continuing. It really requires other popular characters to maintain the audience with one stepping in the new main character role and really good writing. But I really think we are discussing very different things.

My point isnt that changing any actor in a show spells its death but changing the Main character in an ongoing depiction of that character in a show or film does, hence why I chose the examples I chose.

This is the case with Robin was that the show ended one year after. Although it is a UK show and thus they dont really incentivize making 10 seasons like the US, I do wonder what the audience ratings were for the show in the first two series compared to the third.

What I mean is that West Batman can be seen as a different entry to Keaton Batman which is different from Bale Batman and so on. People have their own favorite Batmans, Spidermans, etc. but these actors are in their own reboots and not in the same narrative. This is the same for Sherlock and Bond. RDJ's Sherlock is very different from Cumberbatch and Ferrell or Brett and although they are portraying the same character, the interpretation and world is very different that they are independent, like a parallel world version of that character. I dont know enough about Jack Ryan to comment but it does seem to be similar to Bond in that although the character is the same, the stories arnt narratively connected and you are seeing Ford or Pine Ryan. Change John Krasinski in the ongoing tv show and not be a reboot and the change likely wont go over well. If in the Adam West tv show of Batman, West was suddenly changed with another actor and continued, it wont fare as well.

For Catwoman (and Dumbledore), the point is that the main character of the show isnt being replaced. Dumbledore was due to an unfortunate event and Dumbledore also isnt really in the forefront in the HP movies. Make a setting that Dumbledore is away from Hogwarts and while Harry Potter panics that D isnt there to help, the story can progress without him. There are many examples of this, that 70s show's main character's sister actor changing, Fresh Prince of Bel-Air mom actor changing, etc because they were a supporting character and not always at the forefront. Change Will Smith or Topher Grace (which they did) and the show likely wont last (and that 70s show didnt).

Im not saying that a character can never be recast or portrayed by another actor or the IP is doomed. Thats silly. I know age is a thing and that actors do eventually need to be replaced.

However, replacing or removing the main characters in a currently ongoing show that is supposed to follow the same setting and is not a reboot is very difficult to near impossible, regardless of the actor.

Witcher with Liam in a sense might go over better if they did do a soft reboot of the franchise. There will be another entry into the Witcher and other actors playing Geralt but trying to do so in an ongoing narrative most likely wont go over well.

That third season, that had more episodes than the two previous seasons combined :)
I liked Connery better, while my sister preferred Praed :)

Today the two highest rated episodes are from the second season, when the first Robin died.
The ratings were ok, the show had an open end, another season was planned.
But the studio Goldcrest films got into problems and had to cut the whole thing down
(something similar killed the Elvira franchise).

I get your point.
It's not often that main characters get replaced and that's for a good reason. People tend to identify the role with the actor.
My point was that it can be done.
Here are a few examples where it happened
https://comicbook.com/tv-shows/news/shows-that-replaced-their-leads-and-how-long-they-survived/#9
In some cases it failed impressivly (Batwoman, but that show was garbage from the beginning), in others the production went on as if nothing happened.

In the case of the witcher I don't see much of a problem as long as the guy can look gritty and can follow a choreography. The rest is makeup. I never thought that Cavill was the one carrying the show with his acting.

I also agree with you that its not the ultimate death sentence I initially made it out to be and doing more research, you are right there. Its also hard to say that it is the only factor for a shows death given that there are likely many other factors in play and the reason for a lead actor changing likely has a big influence on the end result (big difference between actor change because the actor left vs actor change because of unfortunate incidents).

Im in the camp that Cavill carried the show. He is a huge asset in drawing eyes to the show, being a Hollywood actor and the biggest name on the show by far. He is also a good actor and has passion for the IP which does help.

I'm actually currious where you found this, since Cavill talked in interviews that, as long as the storyline is good, he'd be willing to play the role for 7 seasons.

I checked multiple sources. Can't remember the exact one, but it was something like screenrant.

That Cavill left the show right after it became clear he will return to the DCU as SUperman is noit a coincidence.