The only reason we can give Valve any time of the day is due to the quality of the service and the fact they're an actual GAME DEVELOPER.
They can make exclusives for their Steam Infrastructure. They can put some push on Sony and MS (high end) if they get their dices rolled in a line
This wont have any bearing on Nintendo even if Valve makes a low entry proposition.
Nintendo succeds and fails based on their own merit with igniting the wonder and interest in their consumers.
See the problem with this is this thing still only appeals to the market base that the Xbox had pre-kinect.Its complex. The fact that Valve has no established market presensce also contributes to this. They have a huge uphill battle, but if they can capitalize on any major shifts in the gaming industry I think they can position themselves well to carry the ball if the others drop it.