There’s recently been a huge shakeup in the Marvel Universe but in a good way. For the first time ever, there’s a very high chance that we could see X-Men characters in the MCU (Marvel Cinematic Universe), thanks to the (huge, unprecedented, somewhat terrifying) merger between The Walt Disney Company and Fox Studios.
While the situation is a little bit more complicated than just one studio taking control of the other, this does mean that many iconic characters are together again under the same Marvel umbrella. And that (probably) means anyone whose dreamt of the X-Men eventually joining the Marvel Cinematic Universe is going to be very, very happy — but not just any time soon.
You might not even realize that the X-Men not being with the Avengers is even a whole thing, but it is. Before it was a stand-alone production studio, in the 1990s Marvel was just a bankrupt comic publisher. In order to stay afloat, Marvel started selling off the rights to some of its most famous characters — so the X-Men went to Fox, Spider-Man went to Sony, and for a while Iron Man was actually at New Line Cinemas (before going to Paramount where the first Iron Man movie was made). And thus, the characters in the Marvel universe separated into their own separate universes on film.
While this helped keep Marvel afloat, and later lead the company to start the Marvel Cinematic Universe, it means that some of their characters are still owned by different studios. The Spider-Man movies — all of them! — belong to Sony (that means Disney, who produces every other MCU film including Avengers: Endgame, actually has nothing to do with Spider-Man: Far From Home except for trying to keep Tom Holland from spilling any more secrets about future projects). There is an agreement that allows the Spider-Man movies to connect to the mostly Disney-run MCU though, so this one comes with an asterisk.
More importantly, until a few months ago, Fox had full control over all of Marvel's X-Men characters when it comes to film. But with the Disney and Fox merger, Disney has managed to gain control over all these characters they don’t have: namely, the X-Men and the Fantastic Four. For the first time since the beginning of the Marvel Cinematic Universe, there’s legitimately a chance that we could (again, someday) see Wolverine fighting alongside the Hulk.
However, this isn’t going to happen anytime soon and it’s not like Professor X is suddenly going to show up at Avengers headquarters. There are currently no announced plans for X-Men characters to appear in any MCU movie, not even via references. There have been no X-Men references to date in the MCU, even if you think Quicksilver (the super-speed character played by Aaron Taylor-Johnson in Avengers: Age of Ultron and Evan Peters in Dark Phoenix) kinda counts. Technically, Quicksilver in Avengers is a totally different Quicksilver, because he’s never referred to as a mutant; instead he’s “enhanced” and yes, this was done on purpose to avoid referencing the X-Men.
But while there will still (officially) be no mutants in the MCU in the near future, these drastic steps to separate the franchises are probably history. Plus, it'd be pretty wild not to see any X-Men later on down the road as "brand new" characters with new storylines in the MCU now that they're all technically family.