Bryan Singer took to the Twitter to announce that X-Men: Days of Future Past would feature appearances by Sirs Ian McKellen and Patrick Stewart, reprising their roles as old-ass Magneto and Professor X. It's unclear how much of the film they'll be in.
Days of Future Past is one of the most seminal X-Men stories. In it we see a dystopian future where giant robot Sentinels hunt and kill mutants. Many of the most popular characters are dead in this alternate, dark future. In the story future Kitty Pryde mind travels to the 'present' to warn the X-Men of an upcoming event upon which history pivots - if they don't stop it, the dystopian future will come to pass.
I wonder how much this movie will be used to do some continuity housekeeping in the X-Men movie franchise. It's a little twisted and the timelines stretch out in weird ways, and a touch of tidying would be nice. Also, if the First Class kids alter the future, it would allow Fox to slyly reboot the X-Men modern day films.
I do hope there's a scene where Old Magneto and Young Magneto appear together and discover an irresistable attraction. I'm sure we could talk Ian McKellen into it.