Maybe its just me but I think the vitality sensor game is going to be something like a "Lie-Detector Party Game" which could be enormously fun and it would certainly be a new experience. That's probably the type of thing Nintendo needs along with Zelda for Oct-Dec 2010 to hit ~3.5m-4.5m in October-December.
That said, I think hardware has peaked in 2008-2009. So for the USA market in 2010 I have this:
DS - 8.75m (-18%) (ahead of 2007, below 2008-2009)
Wii - 7.85m (-12%) (ahead of 2007, below 2009)
PS3 - 3.85m (-9%) (ahead of 2009 until September-Dec)
X360 - 4.00m (-19%) (behind 2009 all year - but less so with Natal over Christmas)
PSP - 2.00m (-20%) (behind 2009, worst year - could be worse if PSP 3000/ PSP Go don't get a price cut)
PS2 - 1.25m (-31%) (worst year, becoming irrelevant)
I think we get PSP, X360, and PS3 price cuts by Summer time. PS2..Sony may just leave it at $100 until it stops selling. Wii/DS will probably see a price cut if needed in the fall. Could see PSP alot lower if DS2 or PSP2 is introduced in 2010 in the USA. But I suspect both are coming in 2011 in the west rather than in 2010.
I keep hearing rumors that X360 will be bundled with Natal for $200 as a sku starting sometime between E3 and November...its success should depend on games but it might force Nintendo to cut price to $100-$150 if it works. That said, some of the momentum may be blunted by Gem and whatever the Vitality Sensor ends up being.