Director Mike Newell, who helms Harry Potter and the Goblet of Fire, has confirmed to Sci Fi Wire that stars Daniel Radcliffe, Rupert Grint and Emma Watson will all be in the fourth film.
Newell is even coordinating with Prisoner of Azkaban director Alfonso Cuarón to make sure his film picks up gracefully where the third ends:
"What Alfonso has done very remarkably is he's developed the films from a sunny vision of childhood into something that is much darker and blacker," Newell said. "And he's done that without taking away any of the romance of the thing. But he has transformed it into adolescence, and I must go on from what he's done. (I) can't go back."
Goblet of Fire is in pre-production and will commence in late April or early May, according to Sci Fi Wire. Newell said that he's currently working on creatures (dragons) for his movie.