FOX and Marvel haven't been on very good terms since Marvel tried producing an X-Men rip-off series called Mutant X, that FOX sued them over. This bad blood pretty much destroyed any hopes of cross-overs between heroes featured in FOX movies and the ones featured in the Marvel Cinematic Universe.
However, rumors are suggesting that the two are working things out.
One of the latest episode of Collider Heroes featured Matt Key, a producer on Kevin Smith's 'Fatman on Batman' podcast, who revealed that he had been hearing rumors about FOX and Marvel talking out their issues:
"I've heard from a few of my sources, my little birds that Fox and Marvel have… kind of talked, but not really, but like there's interest from Fox, like, 'Ooh, y'know, what they did with Sony and Spider-Man is actually pretty cool, like, maybe…' We're years away from that ever possibly happening… but I think that's what it would take… Fox joining hands with Marvel…"
Since Mutant X, there have been some changes at Marvel. The folks that were there for Mutant X are no longer there, the head of Marvel Studios (Kevin Feige) doesn't answer to Isaac Perlmutter (the CEO of Marvel). Basically, Disney's CEO, Bob Iger, stepped in to set Marvel straight.
With the changes at Marvel, there's definitely a chance that cross-overs might happen some day.
