X-Men producer and director Bryan Singer had a sit down with EW and had some interesting tidbits about what is coming after Days of Future Past, namely X-Men: Apocalypse. According to him it will be based slightly on the original Age of Apocalypse event, albeit it will not be an alternate reality. He also warns after credit scene lovers to not expect a huge reveal towards Apocalypse at the end of Days of Future Past. Instead events of the film in general will push the story forward towards Apocalypse.
Other good news is that Xavier, Magneto, Mystique, and Beast will all be back, with the respective actors already signed for the film. They are also hoping to add in new, younger versions of characters such as Nigjtcrawler and Gambit!