Although it’s only rumour at the moment, AICN reports that they’ve had a tip that Fox plans to based the sequel to X-Men: First Class on the classic Uncanny X-Men story Days of Future Past. It appears that name has been registered as a title with the MPAA, giving a good hint that’s where the movie is headed.
What’s particularly interested many about this, is that the time-travel aspect of the Days story means that it could be used to unite the casts of First Class and the X-Men movies.The story arc sees Kitty Pryde getting warned by a future version of herself from an alternate timeline that if they don’t prevent the assassination of Senator Robert Kelly, the mutants will all be incarcerated in internment camps. The X-Men team together to stop Magneto’s Brotherhood from carrying out this plan. That helps bring back a lot of the main cast, those who split off with Magneto at the end of the last film and those who stuck with Professor X, as well as highlighting the conflict between Professor X and Magneto that has been a focus of the X-Men films.
The story alternates between the past and the future, allowing both the First Class and X-Men casts to make an appearance, if Fox can pull that off. However even if they do use this plot as the basis, there’s no guarantee any of the original X-Men will make an appearance. All we have now is that the title has been registered.