This is interesting. We were all wondering what the next X-Men movie was going to be called. Would it called X-Men First Class 2? Or how about X-Men Second Class perhaps? It turns out it’s going to be X-Men First Class Days of Future Past. Probably.
Back in 1981 shortly after the Dark Phoenix Saga concluded there was a two issue storyline with the aforementioned title that made a bit of an impact with X-men fans and affected the x-men comic universe. In a nutshell there is a fairly apocalyptic future for the X-men. in the early 21st century mutants have been rounded up or exterminated. most of the familiar faces from the comic are dead. giant sentinel robots patrol and destroy mutants on sight.
One surviving mutant, Kitty Pryde, manages to send her consciousness back to the then-present of 1981 into her younger self. Her job is to try to convince Professor X and the rest of the team that the terrible future awaits and they have a chance to avert it if they can stop Mystique assassinating Senator Kelly.
So in essence is X-Men does The Terminator storyline, three years before The Terminator hit cinema screens. It will be very interesting to see how this translates to cinema screens. We will find out in 2014.