Wii Music will still reach a million worldwide with ease. Wherever it lands LTD... who knows? The game's going on 200,000 in Japan and I full expect Europe to be the biggest region for the game, kind of like how Wii Fit, Nintendogs, and Brain Age were the biggest there, too.
Given development costs, etc. the game is nowhere near a bomb, but it's also not the "Wii ____" in terms of sales. I'm sure tons of companies would want to invest that amount into a game and have it sell those numbers. Still, this is not the usual Nintendo hit for the holidays. I fully expect Animal Crossing: City Folk to do better, even though it seems like they took the lazy way out on that, too.