I think they will make a DS/Wii version(kinda like there was a DS/Wii M&S) that will come out in August to help fill the Lull between MK and the big unknown holiday titles. Pikmin would be a good choice for this because it would defitily have legs through Christmas.
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut