like i've said before, the only thing MS motion control will kill is Wii Sports (and maybe it won't)
that thing is only for Sports games as it seems, party games as you are calling many Wii games!
Wii is not dead
the MS motion control is really impressing, but if you think of it, it does not really contribute to core gaming, but Wii Remote is used both for core and casual games
buttons cannot be replaced
i would only buy a Xbox360 if an on-rails shooter came out for it, featuring fighting elements and swordplay and this stuff... that would really be a step beyond
the only thing Microsoft motion control can really do that Wii Motion+ cannot is legs movement, Dancing games perhaps?
don't mind my username, that was more than 10 years ago, I'm a different person now, amazing how people change ^_^