To quote Nick Fury at the end of “Iron Man”, You have just become part of a bigger universe. You just don't know it yet”.
The same could be said in this situation, only this would apply to the Marvel movie universe.
ComicBook.com did have the foresight to see that Mandarin would be the next villain to oppose Iron Man in “Iron Man 3”, and while still unconfirmed, they have reported that Tony Stark would have an involvement with “Guardians of the Galaxy” as well.
The rumors can indeed be substantiated because they have been making their way around the Internet and they do seem to be justified based on the events that have occurred up to this point.
For one, Disney’s success with “The Avengers” pretty brought about a light bulb moment of realizing the value of a cohesive universe. Since cross overs constantly occur in comic books, it would just make sense to have the other two studios, Sony and Fox, cross over and join forces.
Sony had plans to create a “Spider Man” universe as well; building its own exclusive cinematic universe and Fox is doing the same with “X-Men”. When Marc Webb had discussed with an online journalist about his dream of building his own “Spider Man” universe, Miller responded, “Think bigger”.
That being said, one might think with all the studios going by the way of their own corresponding universes, fans might be disappointed in seeing their favorite characters joining forces to defeat a foe. Just think of it, characters from “The Avengers” joining forces with Xavier’s forces of the “X-Men” against the Sentinels. In fact, it would simply just be more representative of the actual Marvel universe anyhow.
This all simply ties back to Disney’s success with “The Avengers” so it would stand to reason that this move would just create a momentum of even greater achievement. At this point, there is nothing as quite expected, but one should look for other hints in future Marvel movies to establish that everyone would finally co-exist in the same universe.