I'd totally buy this, and I can see them warming up to the idea as it'd be able to recycle Galaxy's engine (plus up the number of Mario games on the Wii). And along with Brawl, it'd one one of the few games I'd actually like having a level editor for (not that Shiggy said there'd be one), as I just found it fun to jump around in that game. Of course, I wouldn't need it immediately, as I haven't even gotten 70 stars yet in Galaxy.
And I'm also bewildered why New Super Mario Bros. has sold so highly. Yes, it was a new Mario side-scroller on a system with a huge install base, but the game didn't blow me away (I even sold it back, tho I now regret it). They should put out a second one of that out soon, but make it have a little more character next time around (the SMB3 to the original SMB, if you will). Super Princess Peach 2 would be nice, too.