So,I came across an article on SlashFilm.com that you can read here
Kevin Feige himself has confirmed that they have a backup plan in in case some characters rights get reverted back to Marvel. Of course, Feige is referring to :
X-Men and Fantastic Four
According to The Main Marvel Man:
The short answer is: the most important thing is the standalone movie, relaunching Spider-Man with a standalone movie with a new storyline that fits into this universe – that’s job number one for us. And as is the case, the connectivity is great but it doesn’t drive the train. That being said, if I understand what you’re asking, we had… this has been a dream of ours for a long time, and we always had contingency plans should you know — which we always do anyways. Are we going to be able to make another movie with this actor? If we are then we’ll do this, if not, we’re going to do this. If we get the rights to a certain character that’d be great, then we’d do this, if not, we’d do this. So we always sort of operate with those alternate timelines available and are ready to shift if something happens.
It seems like Feige is admitting that they have plans, should they get the rights to some of FOX's superheroes. So, The Marvel Cinematic Universe can pretty much change, right?
It Seems Unlikely
You see, it's unlikely for one franchise to get reverted back anytime soon, and that's The X-Men. First off, it seems like FOX has a long-term plan for the mutants, including finishing Wolverine, restarting the X-Men, Deadpool, X-Force, and whatever else it holds in store for us. FOX will also not be willing to give up a big money maker. Proof? Next year alone they have three projects that are sure to be rolling out the dough for them. Deadpool, X-Men Apocalypse, and Gambit starring Channing Tatum. Now, one thought that pops into my head is after Wolverine 3, FOX parts with the character and he can come back to Marvel, unless they decide to recast him and retell his story. (Hopefully a little bit better)
Don't be too sad though...
Fantastic Four Could Come Back...
After another terrible attempt at bringing the first family to the screen, FOX may give up and leave them be. This potentially leaves not only the Four, but a handful of characters free to come back to Marvel. You have villains like Dr. Doom, The Skrulls, Galactus, and Kang to pose new threats and heroes like The Four themselves, Silver Surfer, Namor (For Real) and more. That opens up stories like Secret Invasion to come to the big screen.