I'm gonna say it right now...I don't think that is the Enterprise crashing at the end. Possibly Cumberbatch's ship? And how would he be Mitchell with Cumberbatch using his natural accent? In this new timeline Mitchell has become British?
If he is indeed a TOS character I'd say look for someone who is British, part of Starfleet and would be "returning" from something. A few other things I noticed...
- Some form of new uniform variant with grey primary and department colors in the little "slits" near the collar.
- Like I said, I don't think that is the Enterprise crashing at the end unless the engines changed from the first.
- It does look to be the Enterprise rising out of the water though. Lots of ships taking a bath in this one.
- Alice Eve's character's (Carol?) scream sounds eerily like the one from the beginning of ST09 when the unfortunate crewmember is blown out into space.
- Cumberbatch is fighting Klingons with what looks to be a gigantic gun or at least something really huge that he's swinging around. Suggests some sort of super strength.