Which add-on will sell the most in 2010?

[CommonMan]

Vetteman94 said:

When are all three going to be released, that will make a big difference as well.

Natal is late 2010, PS Wand/Gem is spring 2010, Wii Vitality Sensor ?????

I believe they said the vitality sensor was 2010, at least hinted at it. Maybe I should have said "in their first year", but I wanted to see if anyone thinks a late launching Natal could beat the Gem, or if the Gem will win by being first, etc.