It's late right now, I've been out all night, and the last thing I want to do is spend lots of time on this 'announcement trailer.' I'm sure it has lots of bombastic blockbuster shots in it that wow the general, Transformers loving audiences, and it has the BWAAAM inception sound on it (to go with the Dark Knight posters).
The footage doesn't exactly tell us who Benedict Cumberbatch is playing, but there's a shot in the Japanese trailer (embedded below) that gives us an idea. It's a shot that looks like it's aping Spock's death scene, with Kirk and Spock separated by glass. The argument against Khan being the villain is that this shot is so much giving it away that it must be misinformation. I've heard from multiple sources that it is Khan, though. I guess we'll wait and see.
For those who will, invariably, complain that I am not falling into line with the 'It's so keeewl!' mindset: a) fuck you and b) I was very cynical about Star Trek 2009 and I gave the film a good review after seeing it. Believe me, I want the movie to be good. But that doesn't mean I'm going to walk lockstep with the 'declaring a film a masterpiece after 60 seconds of footage' fanboy crowd.
Here's the Japanese trailer, with the extra shot that may or may not be the key or the disinfo: