WSJ reporter Kate Kelly identifies the key financial issue for Harry Potter and the Goblet of Fire:

"Factoring in world-wide box-office, home-entertainment, and merchandise sales, Harry Potter has generated some $3.7 billion in revenue for Warner Bros. since 2001, when the first film, Harry Potter and the Sorcerer's Stone, was released. But theatrical movie revenue, while still robust by any standard, has declined moderately with each successive film, with the first Potter film's $318 million domestic gross falling to $250 million for the third movie last year.

"Meanwhile, the cost of making the Potter movies has climbed steadily. And with a $260 million budget on Goblet—which was whittled down to $200 million in actual spending after tax credits—the loss of younger audience members could be painful."

Or not: Warner seems pretty confident that the audience for Potter films is starting to skew older, including teens who've grown up with the books and won't be affected by the film's PG-13 rating.