Marvel movie fans have been trained to sit through the initial end credit sequence for codas/teasers that link the movie to a future Marvel film.  At least when it comes to Marvel Studios films.  It appears that Sony and 20th Century Fox are going to take advantage of that conditioning, with Sony running a preview of sorts for Fox’s X-Men: Days of Future Past after the credits run for The Amazing Spider-Man 2, according to Empire Online.
 
The story broke with the U.K opening of Spidey 2, and Sony has confirmed that the X-Men: DoFP action sequence will run with the American release of Spidey 2 as well.  Educated fans know rival studios license the two heroic properties, which means there is exactly zero chance of an actual on-screen cross-over, and that this is just a clever bit of marketing.  But expect there to be some educational arguments breaking out in the lobby among fanboys who really want to see the X-Men in a live-action Spider-Man and His Amazing Friends movie.