They've stated (somewhere ...in the Ledger interview?) that the movie is about BATMAN. Not the villain. Just like Begins. So, like, the teaser in December (I Am Legend) and the (same) first five minutes of the film will give Joker intro, but the focus will remain on Batman. It looks like they've got a tie between Joker and Two-Face though. All the hints tend to insinuate that Joker will be the cause of Harvey's transformation (even if it is through Maroni).

Old men, fear me! You will shatter under my ruthless apathetic assault!

Uschi - 2
Old Men - 0

"I am convinced that this world is of no importance, and that the only people who care about dates are imbeciles and Spanish teachers." -- Jean Arp, 1921

"If Jesus came back and saw what people are doing in his name, he would never never stop throwing up." - Max von Sydow, "Hannah and Her Sisters"