The latest issue of UK listings magazine Radio Times includes interviews with current showrunner Steven Moffat, outgoing Doctor Who Matt Smith and actress Jenna Coleman. The latter states that the 2013 Christmas Special, The Time of the Doctor, is a "brilliant episode" and "incredibly emotional" whilst also adding that the new Doctor, Peter Capaldi, "certainly makes an entrance!" Similarly, Matt says that it's the "perfect entrance for him."
Moffat chips in: "We'll find out that Matt Smith is actually the 13th Doctor - although everyone knows that the Doctor can only regenerate 12 times. That 12-times limit is a central part of Doctor Who mythology - and science fiction is all about rules, right? So if the Doctor can never change again, what's Peter Capaldi doing in the Christmas Special?"
Lastly, at the BFI Doctor Who at 50 screening yesterday in London, Steven Moffat reiterated that Series 8 would not be split and run continuously. The next series is due to air in August/September 2014.