X-Men: 10 Theories For How They Can Join The Marvel Cinematic Universe
7. They Hail From Another Part Of The Multiverse
Doctor Strange in the Multiverse of Madness is going to follow the Sorcerer Supreme as he travels through the Marvel Multiverse, exploring different timelines and realities...well, that's the prevailing theory, anyway! The What If? animated series will also delve into those, and it really does feel like Marvel Studios is about to expand the MCU in a massive way.
It's possible that as Strange travels through the Multiverse, he will come across a world where mutants exist, inadvertently bringing them into the one he calls home. Who knows, if Kevin Feige really wants to shake things up, the X-Men could arrive in this world from a desolate future...the Age of Apocalypse, perhaps?
That would avoid the need for an origin story, and means that the X-Men who become part of the MCU are completely different to past versions. Some fans wouldn't be on board with this, of course, but Strange's action could even lead to the creation of new MCU which is merged with a world where mutants exist (similar to the Secret Wars comic book event by Jonathan Hickman).