Personally I am exited to see an older and more experienced Ciri walking the path of a Witcher. Contrary to some people here I am not particularly upset to see Ciri as a full blown Witcher that has taken the Trial of Grasses.
As far as I know it's not really against the general lore And before you ask - Yes I own and read all the books in this series, and can actually look at them from here where they sit cozy on my book shelf. But let's be fair - Even Gerald and Jeffifer being alive in itself is already completely against that lore, so in principle all Witcher games are non-lore games (funny how that works).
Anyway - I have always seen the Witcher games as taking place in the Witcher universe, but not a one-to-one translation of those books to game form. They borrowed some things, but also leave out a lot of stuff. In general it's a story, based on a original story, but not the original story itself. So in the end fantasy and creative story telling is more important than being blindly copying the original. And that has worked very well in the past games, and I am sure it will also work well in the upcoming Witcher 4.
As for Ciri being older and a badass. I like that. Mayby some people that cannot handle strong women start crying and hide themself, trembling and all, under some rock. But I am not one of them. Ciri has grown from a uncertain teenager to a full mature woman. I like that, because that is what she wanted, and that is what she has become. I see nothing wrong with that.
Loosing a part of her abilities can be a result of fighting the White Frost. That was a calamity that threatened to destroy worlds and as such was immensely strong, so stopping that would have cost her a lot. I can imagine she took the Trial of Grasses to at least win some of that lost power back. She certainly is not a part of the School of the Wolf, so the other school probably had another trial that was far more fitting to women. And her elder blood would have pulled her trough stuff that would have been lethal to "normal" people. And of course that trial will change her body, face and capabilities.
I can also imagine that Ciri goes on a journey to restore her former capabilities that she has lost to the White Frost. And lastly - Do not forget Ciri can live for a long time. Who knows how may years have past since the previous game. It could be a few decades, but also more than a hundred years. A LOT can happen in such a amount of time.
Sure - The above is a lot of speculation, but it would explain (at least for me) what is going on.
Anyway - I am going to buy this game. I have bought and played all previous games, so I have no doubts about that.