According to Bleeding Cool, X-Men: Days of Future Past will lead directly into X-Men:Apocalypse.
“There’s a clear narrative thread that will string the two pictures together, and the character of Apocalypse is a good part of how this will work.”
They believe that several cast members of Days of Future Past will be wanted back for the film, including members of both the “past” and “present” timelines. They also mention we’ll see new characters as well as old favorites in smaller roles.
No word yet on if Bryan Singer is directing, but it’s more than likely.
Source: Bleeding Cool