Convinced more than ever it's going to be Khan
NOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!
Seriously, I doubt it, and I would be disappointed with JJ if he did that. All we know for now is that the villain is or looks human, and has good reflexes. So maybe he's a vampire and Star Trek XII is a Buffy crossover. Or he's just a well-trained fighter. There are so many possibilities (OK, Khan is a bit more probable than the Buffy crossover) that we should not start panicking now.