If we're talking the Destructoid readership, I'm guessing the answer is "not too many." But still, I wonder how well Wii Play: Motion will sell with the general populace.
The game certainly looks more imaginative than the original Wii Play, which sold extremely well, but I have a hard time believing that will help the game to be a hit. The key to the game's success lies in how badly people want an excuse to buy a Motion Plus-enabled Wii Remote. That trick certainly worked for Wii Sports Resort, but again, can lightning strike in the same place yet again for this brand of packed-in mini-game collection?
I think a lot of that depends on whether or not Project Cafe makes exclusive use of the current Motion+ Wii Remote. If it does, than Wii Play: Motion will have an audience for years to come -- on both the current Wii, and its upcoming successor. If Project Cafe makes exclusive use of some other controller, then I'm guessing that the Motion Plus Wii Remote will join the microphone-controlled GameCube title Odama, and the entire library of eReader card games in the annals of false starts of Nintendo's history.
Wii Play: Motion - first trailer [GoNintendo]