Marvel plans to give Magneto his own comic book series, very noir stuff:
link. The series will, among other things, focus on Magneto's origins, as well as his relationship with Charles Xavier - who is dead again at the moment, in the comic book verse, I mean. So there will be some flashbacks to their early days. That sounds actually pretty cool. I might get even get it!
The next X-Men movie will be called
X-Men: Apocalypse and it will be released on May 27, 2016:
link.
Regarding the plot & cast:
Days of Future Past will lead directly into 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.
Several cast members of Days of Future Past will be wanted back for Apocalypse, including members of both the “past” and “present” timelines.
Source
I have no idea what the whole plot is about, I'm just curious about how they will merge the original and the FC cast again, considering that using time travel twice in the two subsequent movies would be over the top. Maybe the FC people will meet Apocalypse first? Who knows...
Hugh Jackman isn't sure if he will be back for the movie, though. He will be back for the third Wolverine, but he isn't sure about
Apocalypse:
link.
Also, Fox hired Simon Kinberg, the writer of
X-Men: Days of Future Past and the first
Sherlock Holmes movie - but also of
X-Men: The Last Stand *cringes* - to oversee the creation of a cohesive universe, combing X-Men and the Fantastic Four:
link.