They did so via a quick announcement on the Official Site including a photo from today’s cast reading of the script in London:
Actors John Boyega, Daisy Ridley, Adam Driver, Oscar Isaac, Andy Serkis, Domhnall Gleeson, and Max von Sydow will join the original stars of the saga, Harrison Ford, Carrie Fisher, Mark Hamill, Anthony Daniels, Peter Mayhew, and Kenny Baker in the new film.
The big surprises here are Andy Serkis and Max von Sydow. Neither of them were ever rumored to be involved before this.
We’ll be updating throughout the day in case more news comes out.