Fresh off his recent film appearances in Tinker Tailor Soldier Spy and War Horse, Cumberbatch is apparently trading in his Sherlock coat for a black hat, as he will be playing the sequel’s main villain. Nothing further on who or what that villain may be (and how entertaniing is it that we actually have to add in the “what” here, as he could be playing any variety of alien, I suppose?), though if you’re interested in a good bit of incredibly detailed speculation, the internet is more than happy to provide that sort of thing for you.
Clarke is probably best known for his role as Mickey Smith, the boyfriend to Billie Piper's Rose Tyler on Doctor Who, though he has written, directed and starteseveral films (Kidulthood and Adulthood) since his time in the TARDIS. No word yet on what character he will be playing for Abrams’ film, though Variety reports the role is a “family man.” (I don’t know enough about the Star Trek world to hazard a guess, unfortunately!)
The Trek sequel is slated for release on May 17, 2013. And writing it out like that makes it seem very far away indeed, doesn’t it?