The Simpsons will definitely be #1, and most likely by a wide margin. I guess Hairspray will have a shot at #2, although HP will probably still be strong since most Potterphiles will have finished the book already. I hope/expect C&L to lose some momentum since The Simpsons will probably draw from the same audience.
"It does me no injury for my neighbour to say there are 20 gods or no god. It neither picks my pocket, nor breaks my leg."
-- Thomas Jefferson