Despite all the rumourmongering about a WiiHD, I've got to think the obvious choice would be a DS2. DS has already passed saturation point in Japan and they're basically just getting people to upgrade to newer models/colours to maintain sales. But that can't last forever. Japan needs a new portable by the end of 2010 or sales will really start falling. I'd also expect Japan at least to be getting a PSP2 this year as well.
A revision of the Wii isn't out of the question entirely, and a dvd-upgrading Wii HD is a possibility I suppose as long as it's 100% compatible with current Wii games. It would also allow Nintendo to build WM+ right in to those systems as well. WSR could be the pack-in with Wii Sports sold independantly for $30. Hmmm.... Zelda HD? But still, I doubt it.