IGN has an interview with Bryan Singer (The Usual Suspects, Superman Returns) where he states that the X-Men: First Class sequel will be based on the revered comic Days of Future Past.  Have a look at the video, and I’ll be back after:

I loved, loved, loved X-Men: First Class and cannot wait to revisit that universe.  I find it intriguing that they are planning on tying the X-Men universe together (let’s forget that X-Men: The Last Stand exists, shall we?).  This is what Wikipedia has to say about the Days of Future Past storyline:

The storyline alternates between present day, in which the X-Men fight Mystique’sBrotherhood of Evil Mutants, and a future timeline caused by the X-Men’s failure to prevent the Brotherhood from assassinating Senator Robert Kelly. In this future universe, Sentinels rule the United States, and mutants live in internment camps. The present-day X-Men are forewarned of the possible future by a future version of their teammate Kitty Pryde, whose mind traveled back in time and possessed her younger self to warn the X-Men. She succeeds in her mission and returns to the future, but despite her success, the future timeline still exists as an alternative timeline rather than as the actual future.

This sounds really interesting.  As an old comic book nerd, I had heard of the story, but haven’t actually read it.  According to the video, they start filming in a couple months.  I cannot wait.  This could be super cool!