I think it'll force Sony (more than Nintendo) to be aggressive in coming up with some new and compelling ways to interact with our games.
Nintendo is already down that path starting with the Wii so they'll simply continue the course they're on.
As for sales, who knows. This gen has been amazingly sustainable for all 3 and profitable for 2 of them. 2nd and 3rd place consoles will likely end up selling more than any has before and better than some 1st place consoles.