New director Bryan Singer (see "Bryan Singer to Direct 'X-Men'") announced via Twitter that Patrick Stewart and Ian McKellen, who played Professor X and Magneto in the first X-Men movie trilogy, will appear in the sequel to X-Men: First Class, X-Men: Days of Future Past.  That’s going to make things a little crowded, as he also revealed that James McAvoy and Michael Fassbender, who played the same characters in X-Men: First Class, will also return.  The storyline for the film involves an alternate future (see "It's 'Days of Future Past' for 'X-Men: First Class'"), so we assume it will all make sense.

Singer also Tweeted that Jennifer Lawrence and Nicholas Hoult are returning for the sequel.

The film will release July 18, 2014.