I Am 7-Minute Dark Knight IMAX Prologue?

Are you itching to see some footage from The Dark Knight? Omelete is reporting that Warner Bros plans to release a 7-minute prologue to The Dark Knight in front of the IMAX screenings of I Am Legend on December 14th. The footage will apparently feature Heath Ledger as The Joker. But remember, the 7-minute prologue will only be attached to the IMAX version (which I'm assuming is a cross promotion since Dark Knight will also premiere on the huge IMAX screen). We'll try to find out more details.