According to an extremely reliable source, Harry Potter and the Goblet of Fire will have a running time of 157 minutes, making it the second longest film in the series of Warner Bros. adaptations of JK Rowling's books. The second movie, at 161 minutes, is the longest.
We're awaiting confirmation from Warner Bros.
UPDATE: WB cannot confirm the running time at present, but The Leaky Cauldron is also reporting they've received tips that the film will be 160 minutes.
UPDATE #2: According to another tipster, the film is "2 hours 34 minutes and 38 seconds or 154 minutes and 38 secs... from the first glimpse of the movie until the last frame (WB logo)." Presumably, that figure is based on an advanced cut of the movie.