Sorcerer's Stone = Worldwide: $976,475,550
Chamber of Secrets = Worldwide: $876,688,482 DOWN 100 MIL
Prisoner of Azkaban = Worldwide: $789,804,554 DOWN 90 MIL
Goblet of Fire = Worldwide: $892,213,036 UP 100 MIL
Based on the book's story (i've read it) and the previews of the movie (and the reviews of the sneak previews) i believe this next movie may pass the $1 billion mark worldwide. And also, people who own a PS3, 360, and a Wii will definitely prefer the Wii version (OMG YOU CAN USE A WAND!!!)
Atleast, thats what I'm stickin by. This will be the first Harry Potter game that I actually buy for myself (and not my 6 year old nephew). Also, the game's mechanics have totally been re-done (GTA-style missions, you can basically explore the whole Hogwarts campus willy nilly).
So, in conclusion, the Wii version will sell 2 million copies before January 2008.