According to The Leaky CauldronHarry Potter producer David Heyman commented that he was “cautiously optimistic” when asked during a Q&A session at the DVD launch for Harry Potter and the Prisoner of Azkaban that Daniel, Emma & Rupert would be returning to film the next movie.
Are you going to replace the three leads [for HP5]?
Heyman: I hope not. The kids are on for the fourth. We now will start discussing the fifth, it's the same on each film. You're in the middle of the third you discuss the fourth, you're in the middle of the second, you discuss the third. I hope they stay with us and they'll stay with us as long as they want to. There may come a point some day where they decide not to and if they do, they'll go with all of our blessings. But I hope they stay and they're wonderful, and I'm cautiously optimistic that we'll have them again for five.