I'm just not sure. It seems a fantastic idea and utilisation of the device, but as you say; at what cost? If it's fortunes, then I deffo wouldn't be intrested but it really depends ( as always ) on clever marketing, product support and price.
PS3 stupid neon bobble stick, with it's constant calibration faults, is just a BAD idea I think that must have been rushed out to compete with Nintendo. It failed.
Xbox kenetic seems to be gaining some ground though. Haven't physically tried it myself, so can't fully comment, but I hear intersting things about it and not many negative either.
So it could seem, if Nintendo do it right they only have xbox to have a fight with????
Kinnect is pretty cool, although at the moment the games are very child based. The company that MS got to make kinnect are also due to release a PC version shortly, so could see this swamping the market.
The roadmap for the future is to also start using kinnect for tasks other than gaming, general use of PCs, TVs etc. I think its going to be the future.