it would be a pretty good decision to "follow" ATi's direction and cheat at making a faster card. :P I use "cheat" because their cores aren't faster but they strap two together, and make it better. nVidia should do the same, and it may not be as cheap; but nvidia could work towards making their chips cheaper to create/more efficient.

I'm personally a bit of nvidia "FANBOI!" but I have to say, this monopoly that they've had on the market is bad, bad, and REALLY bad. Everyone knows competition drives performance, nvidia got way to comfortable at the top and let it slide. ATi was there to bite them in their ass, for assuming that they would always be on top of the GPU market.
To sum my post up, nvidia is probably going to pull a GTX280 GX2(or it's equivelant), or some kind of GTX280 Ultra... I really want these ATi cards to perform better though, or else nvidia won't have to wake up and smell the coffee.