The recent Dark Knight teaser trailer left a lot of people wanting, with little evidence of The Joker, aside from a couple of lines of dialogue and a bit of cackling. Those same fans should be well sated when they go to see Will Smith vampire* movie I Am Legend.
Rather than another trailer, Warner Bros will release a 7-minute scene which will tell the origins of The Joker, but only at IMAX screenings. This is not a collection of footage from throughout the film; this is an extended scene of how mild mannered Heath Ledger becomes the scar-faced clown. So the film will not be an origin story. We couldn't get 100% confirmation, but it seems very likely that this will one of the scenes that was previously announced (read about that here) as being shot in the mammoth scale IMAX format. USA Today said that one of those took place during a bank heist that introduced The Joker. That's not definite, just very likely.
So, we can all get our first look at the latest villain in motion when I Am Legend bows on January 4.
*The filmmakers say the 'monsters' in this film are infected people, not vampires, but they definitely had highly vampiric tendencies in the book.