The Aluminum Falcon said:

Sixth or third, I would guess. Those are the times the Doctor has regenerated to an older looking version.

If I were a betting man, I'd say that the 12th would be of the same ilk as the 6th, who was the same ilk of the 1st.

That's my though as well. Which, by the way, I'm not really looking forward to. That's one of the things that kept me from really connecting to it as a kid. Having a Doctor who is older than me doesn't really interest me. 30s and 40s is fine and has worked really well the past three Doctors. I hope I'm pleasantly surprised.

I also don't see how Clara is going to fit in. Don't know why and it's based on nothing at all at this point (obviously). Again, hope I'm pleasantly surprised. She's become one of my favorite companions. Love her depth and independence.