At this point, all we know about X-Men: Apocalypse is that Bryan Singer is directing for a 2016 release, and that the story will be set in the 1970s, following the younger cast of X-Men: First Class and X-Men: Days of Future Past.
Last night, Bryan Singer sent out a photo of a late-night story session, which showed the director working with writer-producer Simon Kinberg and X2: X-Men United writers Dan Harris and Michael Dougherty.
The filmmaker's reference that it's "snowing in Egypt" could mean that part of the story is set in the African country, which is the birthplace of En Sabah Nur, a.k.a. Apocalypse, in the original Marvel comic books.
Although no story details have been confirmed, the title is a reference to a 1995 comic book arc entitled The Age of Apocalypse, which is set in an alternate reality caused by timeline interference. Professor Charles Xavier was murdered before he could even form the X-Men in this timeline, with Magneto leading a different team in a world ruled by mutants.