Alice Eve looks like she could be a young Carol Marcus or the blonde from the Mitchell episode.
If he is Gary Mitchell, I'm not sure why he's leaping around doing kung fu, getting punched by Kirk and carrying what looked to be some kind of minigun. Or what he would want to "take revenge" upon the Earth for. But if he's Khan, or perhaps one of Khan's lieutenant, that all makes immediate sense.
The Japanese trailer has a little more footage at the end, with a very recognizable callback.
If I had to place odds on it I'd favor Mitchell, though.
The shot of Cumberbatch in a cell has me really hoping this isn't yet another "villain gets caught but that was All PART OF THE PLAN all along" twists. There's been enough of that in recent years.