TV Guide has an interview with Dan where he talks about splitting Deathly Hallows into two films.

“It’s a really positive thing,” the actor told TV Guide during a call to promote Masterpiece Classic: My Boy Jack (airing April 20 on PBS). “And I think the fans will appreciate that more than had we tried to make it into one film. We’d have to cram so much in there and actually have to skip over some things. And in this seventh book, there are a lot of things you can’t afford to skip over.”

The timetable for the big finale? “When I finish the sixth film [Half-Blood Prince], which I’m shooting now, I’ll take some time off — I’m doing Equus on Broadway — and a while after that I’ll get on the Hallows films, which we’ll film as one. That will begin early-ish next year.”