According to this report on VR-Zone their is a good chance that NVIDIA’s next generation chip will be a die-shrunk version of the G92 architecture.  The current G92 runs on a 65nm process as the 8800 GT and 8800 GTS 512MB cards and a 55nm revision would likely bring higher clocks and lower power – always a plus. 
VR-Zone has learned that Nvidia is preparing to shrink G92 process technology from 65nm to 55nm to better compete against the upcoming RV770. DigiTimes today reported that RV770 will come along by end Q2 which is about the same timeframe as the 55nm G92. Most probably, you will see RV770 based mobile parts first as notebook makers have already received RV770 samples for testing. Right now, we are able to confirm some 55nm G92 mobile parts coming up to pit against the 55nm RV770. Most likely, there are 55nm G92 for desktop parts too as Nvidia in desperate needs to lower cost and improve yield in the next couple of months ahead to stay in competition. In any case the 55nm G92 even with higher clocks can’t match up against RV770, Nvidia will have to push ahead the schedule of next generation GT200.