It looks like Peter Capaldi’s Doctor is going to have a new attitude. From Steven Moffat:
”The last two Doctors have been ‘your boyfriend’ Doctors. It was time for the show to flip around. The new version of the show is quite old now.”
“We’re going to give Clara a Doctor who is a much older, fiercer, madder, less reliable Doctor who leads her a merry dance.”
He also hints at a possible return of River Song:
“I’m slightly tempted, because I imagine Peter Capaldi and Alex Kingston would be absolutely hilarious together. She could certainly have met other Doctors. So there’s nothing stopping us … But is there anything new we can do? Or is the new thing that Peter Capaldi and Alex Kingston would be very sexy together? Is that enough? We’ve always had fun with the fact that they don’t look like a couple.
“Peter Capaldi and Alex Kingston would look like a couple — that’s the thing. Whereas I thought Matt [Smith] and Alex were gorgeous together, but it looked slightly strange, because he was so much younger.”