Currently Online 
Soundwave on 26 October 2009
I see it coming in fall 2011. They'll just continue to support the current Wii through 2012 though at least IMO.
For people who want a higher end system, they'll have that option. It will be an additional profit stream for Nintendo as well.
I think actually they probably have the Wii 2 hardware 100% finished more or less right now. ATi or Nvidia could give them a 360/PS3 level chipset no problem obviously. They probably are really working on the interface.
Miyamoto said he doesn't like the Natal concept without tactile feedback, but he did express interest in that type of thing combined with a motion sensing wand controller for instance. Who knows what else they've come up with.
