Steven Moffat has given an interview as part of the Gallifrey One 2013 convention in Los Angeles. In the interview with Ed Stradling Moffat mentions the new Ice Warriors, the return of the Zygon’s and the Master…
Most importantly though he almost definitely denied that there would only be a 1×60 minute special for the Anniversary of Doctor Who in November, saying that it was “complete nonsense”. He also confirmed that there would still be a Christmas Special this December, as well as stated boldly that Matt Smith would be the Doctor “for the rest of time…”
On the Ice Warriors he revealed that:
Mark Gatiss had been pitching the Ice Warriors for a while. I wasn’t tremendously persuaded. I thought they were maybe the default condition for what people thought of as rubbish Doctor Who monsters: things that moved very slowly and spoke in a way that meant you couldn’t hear a word they said. I thought maybe that was the definitive rubbish one. But then Mark came up with a couple of very clever ideas. It’s an absolute cracker of an episode.
Source: Ed Stradling’s Interview