In a USA Today article talking about the IMAX 3D release of Superman Returns, the newspaper mentions that Spider-Man 3 won’t be getting the same treatment:
Sony says Spider-Man 3 is pretty much out of the running (“We’re just trying to finish the movie,” Bruer says), but Warner Bros. could cast a dimensional spell over Harry Potter and the Order of the Phoenix, already booked into large-screen theaters for July 13 next year.
Somehow we think that when it comes to box office figures, this won’t matter too much.
Source: USA Today