Harrison Ford, Carrie Fisher, Mark Hamill, Anthony Daniels, Peter Mayhew, and Kenny Baker are confirmed returning.
John Boyega (Attack the Block), Daisy Ridley (Scrawl), Adam Driver (reported earlier), Oscar Isaac (Inside Llewyn Davis), Andy Serkis (every other franchise we like), Domhnall Gleeson (Bill Weasley in Harry Potter and the Deathly Hallows), and Max von Sydow (Ming from Flash Gordon!) are also cast.
I think it's safe to assume that Serkis plays an alien and von Sydow is either a Jedi master or Sith Lord. Beyond that...who knows? Let's speculate anyway.
Starwars.com and Facebook are practically crashing over this, while social-concern bloggers are already up in arms that only one of the announced actors is female.