Have X-Men Existed In The MCU All Along?
Before there was Disney's massive, interconnected Marvel Cinematic Universe, there were standalone Marvel superhero films – or at least, standalone Marvel superhero film franchises. Prominent among such was New Line Cinema's "Blade" trilogy, Sony's "Spider-Man" trilogy, and then subsequent "Amazing Spider-Man" duology, Sony's "Fantastic Four" duology, and Sony's "X-Men" franchise, which led to so many movies that it was essentially its own micro-universe. In recent years, Disney purchased the rights to all of these properties, allowing them to merge with the greater MCU.
And they are merging. Disney announced a new "Blade" film starring Mahershala Ali, a new "Fantastic Four" film (no further details yet), and even introduced both of Sony's Spider-Men (Tobey Maguire & Andrew Garfield) as multiverse variants of Tom Holland's Spider-Man in "Spider-Man: No Way Home." With such a gung ho attitude towards bringing these characters into the Disney fold, it's somewhat surprising that so little has been officially announced in regards to the newly acquired "X-Men." It seems that "Doctor Strange: Multiverse Of Madness" will show us our first X-Man character with the arrival of Professor Xavier (Patrick Stewart & James McAvoy), and so far, that's all we know.
Disney has tip-toed around the concept of mutants, Marvel's canonical term for humans who naturally evolved to possess great powers, for years now by introducing "X-Men" characters such as Scarlet Witch (Elizabeth Olsen) and Quicksilver (Aaron Taylor-Johnson) and referring to them as "miracles," and now that Patrick Stewart is legally and literally in the mix, we can't help but speculate as to how it'll all tie together.
It's a fun idea, but not very likely
The terminal struggle faced by mutants is one of acceptance. In the "X-Men" franchise we see mutants – humans – terrified to reveal their abilities for the fear of ex-communication or violence, so it's a possibility that Disney will reveal mutants to have been hiding in the background, lurking outside of the spotlight for their own protection. This seems unlikely, though, because most mutations aren't easily disguised, and suggests that Beast (Kelsey Grammer & Nicholas Hoult) could go under the radar in the well surveilled MCU. Not to mention an entire school of super-powered teenagers, which could introduce a significant plot hole. Furthermore, the X-Men's primary antagonist, Magneto (Ian McKellen & Michael Fassbender), is a holocaust survivor, and with each passing year, an MCU set in the current day becomes harder pressed to show a living Magneto from that time period.
There are two other possibilities that seem far more likely. It's possible that some future event in the MCU will trigger a global change and thereby instigate the creation of super genetic mutation. Considering Thanos (Josh Brolin) simply snapped his fingers and changed the entire universe, this isn't really that much of a stretch. The other possibility is that, like Sony's Spider-Men, the X-Men will be dragged into the MCU via multiversal tampering. Now, that doesn't necessarily mean that they'll be portrayed by their original (or prequel) actors. Just because Patrick Stewart is some version of Professor Xavier doesn't guarantee Hugh Jackman's Wolverine or James Marsden's Cyclops. After all, one multiverse variant of Loki is literally a crocodile. Ultimately, we believe the answer to the X-Men's origins will be hinted at, or fully revealed, in "Doctor Strange: Multiverse Of Madness."