The writer told New York Magazine that he is currently writing the episode where River Song's (Alex Kingston) true intentions towards The Doctor (Matt Smith) are made clear.
"Well, you will find out who she is and what's going on and how it all makes sense. And that will explain a number of things," he said. "I'm writing the episode right now where The Doctor finds out who she is. We're not just going to endlessly tease."
Moffat also admitted that he is reluctant to kill off any of the long-running sci-fi drama's popular characters.
He explained: "In the old series, they did off a couple of them. I'm not saying we'll never do it, but it's not that kind of a show. It's not gritty. It's kind of a lovely, life-affirming, optimistic show without a cynical bone in its body.
"It's almost odd when you see it in competition with things like Battlestar Galactica, and you think, 'Well that's not us at all.' We're the story of a wonderful man from space who can travel in a telephone box! But I'm not guaranteeing I won't kill someone in the future!"
Doctor Who returns for a one-off special at Christmas and for a sixth series in spring 2011 on BBC One.