They seem to be coming back. Pantheon, OSRS, Monsters & Memories, Project Gorgon, Adrullan Online - to name a few.
The playerbase for this style of MMOs seems to be aging quickly, and a 40-year-old doesn't necessarily have time for a game where you have to corpse run and spend 2 hours looking for a group. Are younger gamers interested in a return to form?
I personally miss the days when MMOs felt like a world to explore, almost a virtual chatroom, and not just a front for a cash shop. Modern internet will never let these games feel the same, sadly, with Discord, streamers, and YouTubuers.
I will probably dabble in the few coming out in the near future, but to be honest, I didn't even like grinding on worms around a lake for 3 hours in FFXI back when it was new. I think I'm more interested in RPG systems in an online world than nostalgia.