If and when the Disney/Fox deal goes through Kevin Feige has a Hell of a job on his hands fitting the X-Men and Fantastic Four into the MCU. While he's currently too busy with Avengers: Infinity War and Avengers 4 to worry about what may happen, clearly there will need to be some plan in place. Infinity War directors the Russo Brothers think they have an idea that might work, and I actually agree with them.
In a recent interview the Russos suggested the interdimensional crossover Secret Wars could be a way of bringing the various universes together. They said, "If Disney's takeover of Fox goes through, there are a lot more characters to work with all of a sudden, it might be interesting to do something like Secret Wars."
Sounds like they mean the most recent version of Secret Wars, which saw heroes from many alternate realities come together in one massive storyline. It could work, but the mere fact they mentioned it means it probably has no chance of happening. Besides, I'd much rather see the X-Men introduced in a way that gives them the full spotlight, not in some huge crossover event.
