Marvel is all geared up to release four movies -- "Deadpool," "Captain America: Civil War," "X-Men: Apocalypse," and "Doctor Strange" -- this year. Out of these four, "Civil War" and "Doctor Strange" belong to Marvel Cinematic Universe (MCU).
The MCU project has been one of the most successful ventures of Marvel Studio ever. The Phase One and Phase Two movies garnered immense popularity and made great box office collection with movies like "Thor," "Iron Man," and "Avengers."
This encouraged the studio to come out with more movies based on Marvel comic book characters.
Recently, one of the biggest additions to MCU was Spider-Man, the rights to which were previously owned by Sony Pictures.
Fans of superheroes across the world had been speculating whether Spider-Man would ever be part of MCU or Avengers. Sony and Marvel reached an agreement to make the prospect a possibility and now, Spider-Man would debut in "Civil War" before featuring in his own solo movie in 2017.
Similarly, several rumours have been doing the rounds on the Internet, hinting at X-Men joining MCU after "Apocalypse." Though it sounds too far-fetched for now, there is a significant possibility of it, given the reputation of MCU movies and how it has established itself as one of the biggest movie universes of all time.
In comic books, X-Men play a major role in the "Infinity War" story arc. Hence, it will be a reasonable move to include the mutant team in movie universe too, as it would be closer to the original storyline.
However, Movie TV Tech Geeks has reported that as the future MCU movies have been announced till Phase Three, it is highly unlikely to see X-Men joining MCU anytime before initiation of Phase 4. Hence, it will be rare to see any of Professor X's team members in the upcoming Avengers movie titled "Avengers: Infinity War."
Whether X-Men would become part of MCU or not, their addition would definitely add up to the already popular MCU.