As long as the ROMS are cheap and sold in packs I don't object.
I would gladly purchase a legacy bundle pack of all 6500 old late 80s/early 90s Amiga games I know about for 500 bucks or more, even though 99% of the old license rights holders don't even care or know and if they know they would release it for free (as they did before).
Some of those games are...rare to say the least. I know about games on that platform perhaps only perhaps 50 or less people know about, some good stories I could share as well.
Bringing Retroarch to Steam might be a good way for big publishers to understand the mass appeal even further regarding these older games. It took a while for Disney to publish their stuff on here for instance.
DadJoke007: I foresee tons of lazy roms getting "ported" with some achievements and cloud save slapped onto them.
Realistically, just releasing the games without the achievements is probably the most realistic case. Most console re-releases of older games are lazy jobs or license hell after all.