I think it really depends on what "doing well" means ...
The Playstation Move may sell as well if you're thinking in terms of videogame sales or attach rates; but when you start looking at it in terms of sales of platforms it will (likely) do abysmally bad. While I will wait until it is released to comment on Kinect's sales, it could be in a very similar position.
Basically, selling 10 Million units is amazingly impressive for a game but isn't that impressive as a platform; and unless gamers show an unusual interest in buying games that support these platforms it would translate to support for them (qucikly) drying up. Effectively, consider this from a publisher or developer's perspective, you need to decide where to take resources away from because your game is over-budget and behind schedule where do you take it from; you can remove/reduce online multiplayer or local multiplayer, scrap single player components or release a less polished experience, or not implement meaningful features for an add-on that only 1% of the userbase has and regularly buys games for?
