Next Nvidia high end chip will be the G81 and 65nm
 

THE G80 replacement looks like it might be known as G81, and it appears that Nvidia will take the radical step of making it at 65 nanometre. That is what's been rumoured in China and Taiwan and according to sources close to or inside TSMC.

http://uk.theinquirer.net/?article=37199

and when will this be?
don't wanna upgrade to 8800 gtx with something looming around the corner

end of year