Admitting that Move and Natal manage to "steal" some motion control market share from Wii, Wii HD wouldn't be enough to counter them.
But even in the worst case, by the time Wii will dive under 120k/week average during slow periods, it will have sold more than 100M units, in a record time too, so Wii success won't be disputed anyway.
I agree anyway that Nintendo will launch Wii2, Zii or whatever it will be called, before Wii's momentum fades too much or competitors get too strong (if it will ever have chance to happen this gen), that is it won't allow Wii to lose 1st place, at least WW and yearly (and even less as total lifetime sales), before its successor is launched.
I don't believe, anyway, that Nintendo isn't worried at all, because Wii's and DS' success is so huge and unprecedented that repeating it won't be easy.
About Vitality Sensor: it will sell at least like Virtual Boy, but will it sell games?
