2 things. nintendo does not and will not have the capacity to produce enough wii's to hit that. the ds is destroying the wii and it wont get to even 200 million because of production as the limit.
the other is that the audience still isnt quite there. fringe markets might start coming into view (china, india, etc), but video games wont be able to break into them enough to make a difference. it should take at least this gen and one more before they actually matter.