As excited as fans are to see the X-Men join the MCU, Marvel would be wise to wait until Phase 5 to bring them into the fold. The Marvel Cinematic Universe was a novel approach to blockbuster filmmaking when it was first conceived, one that's resulted in unprecedented levels of critical and commercial success. So far, the 17 entries into Marvel's shared universe sport an average 83% fresh rating on Rotten Tomatoes, and they've combined for a total haul of $13.5 billion at the worldwide box office. Earth's Mightiest Heroes have quickly become Earth's Mightiest Franchise, but even the MCU's most fervent supporters have had trouble ignoring the elephant in the room. Plainly put, a cinematic universe based off of the heroes of Marvel Comics is incomplete without the X-Men. (And, to a lesser extent, the Fantastic Four.)
So when Disney/Marvel was finally able to reacquire the film rights to those characters from Fox, fans went nuts. At long last, the MCU has access to Marvel's First Family and the mutants that shaped the comic universe as we know it. The only question that remains is how and when these superhero teams will be introduced.
That's where things get a bit messy. Between narrative complications, various regulatory committees, and the litany of projects already well into development on both sides of the aisle, bringing these beloved heroes into the MCU will not be as straightforward as fans might've hoped. It can (and likely will) be done, but it's going to take some patience. Here's why Marvel Needs To Wait Until Phase 5 Before The X-Men Crossover.
The deal hasn't actually been completed yet
When the deal between Disney and Fox was "completed" in December, most fans assumed that the X-Men and the Fantastic Four would be jumping into the MCU in short order. Why wait to give fans something they've already been waiting years to see, right? Because while the deal has been agreed to by the two companies, it still hasn't hasn't been approved by the proper regulatory committees. Governments both at home and abroad are expected to submit this agreement to the same sort of scrutiny that the 2016 Time Warner/At&T deal was subjected to (a deal that the U.S. Justice Department is currently suing to block, by the way). TLDR: Marvel's purchase of Fox hasn't actually been completed just yet, and it's not quite a sure thing, either.
A lot can go wrong in the 18 months that the regulatory process is expected to take, so the companies have financial agreements in place in the event that one of them ends up backing out of the deal or that it's blocked. But since there's a lengthy road ahead to the deal actually being finalized, the MCU and Fox will continue operating autonomously. Neither company can afford to assume that the deal will be approved, so until it actually is, both Marvel and Fox have to operate as though it's not happening. Marvel Studios president Kevin Feige may be excited to work with the X-Men, and he can (and will) concoct a gameplan for introducing them, but he'll have to wait at least another year and a half to actually do it. Neither company will be sitting on its hands in the meantime, though.
- Avengers: Infinity War / The Avengers 3 (2018) release date: Apr 27, 2018