The thing is, I don't see Kinect being successfully globally or in markets that would affect current trends apart from maybe the US.
In the US I can see it selling well, and I think it could help MS get 360 to a more general audience, thereby closing of some of the Wii's market share a bit and helping to keep PS3/Move in the less dominant position.
But... in Europe I just can't see it being that big a success. The space requirements are just hugely against it. UK is a great market for 360 but terrible for room space. This, plus the fact Move launched first and PS3/Wii are far more dominant than 360 outside UK convince me it just won't make much difference in this key market.
In Japan I think it has no chance. The space issue plus 360 popularity I think will kill it at birth. Sure, there'll be an initial bit of hype, but it'll die quickly I think.
So, while I do think Kinect will be a success I actually don't think Wii and PS3 look to be hugely affected unless Kinect manages to overcome what I see as issues that will hold it back outside US.
Try to be reasonable... its easier than you think...
