Soundwave on 31 May 2009
My guess earlier was (note this is PREDICTION, but this was even before Nikkei semi-confirmed this):
Wii Super Mario Bros.
Runs on Galaxy engine, but has a new 2-player co-op mode for Mario + Luigi + Yoshi + etc. and more retro-ish Mario throw backs.
Zelda: Ocarina of Time and Zelda: Majora's Mask were two years in between. Quite frankly it's about time Mario got another installment more quickly. To take an engine like Super Mario Galaxy and to just junk it until the next console comes out is really terrible resource management.
