Update:
From Kotaku:
"Nintendo just announced that Super Paper Mario will be hitting the Wii on April 9. The game was originally set for the Gamecube, but wouldn't that be silly. Yes, we need some straight up classic Mario action on the Wii. Hopefully this game wasn't already nearing completion when they made the shift. I guess we'll know in a few months. Brian Crecente"
http://kotaku.com/gaming/nintendo/wii-super-paper-mario-dated-235822.php
Update 2 (Thanks ScrubKing):
Some Q&A via 1up.com
http://www.1up.com/do/blogEntry?bId=7895316&publicUserId=1002415
From Kotaku:
"Nintendo just announced that Super Paper Mario will be hitting the Wii on April 9. The game was originally set for the Gamecube, but wouldn't that be silly. Yes, we need some straight up classic Mario action on the Wii. Hopefully this game wasn't already nearing completion when they made the shift. I guess we'll know in a few months. Brian Crecente"
http://kotaku.com/gaming/nintendo/wii-super-paper-mario-dated-235822.php
Update 2 (Thanks ScrubKing):
Some Q&A via 1up.com
http://www.1up.com/do/blogEntry?bId=7895316&publicUserId=1002415