After Fox's earlier X-Men films, the role of Charles Xavier was gradually passed on to James McAvoy. With the Marvel Cinematic Universe rumored to be bringing back the mutant team, there are hopes that the old cast will return. McAvoy, however, is not eager to step into the suit and chair of Professor X.
In an interview with Collider, McAvoy explained, "I feel like, yeah. I feel like I got to explore, not everything I wanted to explore, because there's always more, surely, but I got to explore a ton of Professor X, and I feel quite satisfied with what I got out of him as a performer." One the prospect of being asked to return, he added, "It's not to say that you don't ever want to, you never want to come back, and you never want to do it again, and all that kind of stuff. You never say never, as I believe James Bond once said. But I'm not chomping at the bit. I'm not going to be gutted and desperately sad if it never happens again."
Fox's franchise began with 2000's X-Men, which spawned a trilogy that eventually spawned a much larger franchise. The leader of the X-Men, Professor Charles Xavier, was originally played by Sir Patrick Stewart. The character was killed off in X-Men: The Last Stand, though he made a cameo appearance in X-Men Origins: Wolverine before The Wolverine resurrected him. By that time, a younger version of Charles Xavier was being played by McAvoy in X-Men: First Class. The two iterations met in X-Men: Days of Future Past, which marked Stewart's final performance as Professor X.
McAvoy last appeared as Professor X in X-Men: Dark Phoenix, which was the franchise's final release, owing to Disney's acquisition of 20th Century Fox. The acquisition left several projects dead in the water, such as the Gambit film with Channing Tatum attached.
There has been a lot of speculation concerning when and how Marvel Studios will introduce the X-Men to the Marvel Cinematic Universe. While Disney+'s WandaVision toyed with fan expectations through Evan Peter's return as a version of Quicksilver, the multiverse was firmly established thanks to the events of Loki, Doctor Strange and the Multiverse of Madness and the upcoming Spider-Man: No Way Home.
At least one part of Fox's X-Men universe has already been confirmed as part of the MCU. Deadpool actor Ryan Reynolds confirmed his involvement in the MCU in an ad with Thor: Ragnarok's Korg. Marvel Studios President Kevin Feige then confirmed that Deadpool 3 is in development, though an official release date has not been announced.
Source: Collider