If FUD Zilla is right NVIDIA will not release a 55nm GT200 chip at NVISION last week. The site claims the launch is set for Q4 2008 and heard this new chip will have GDDR5 memory and be faster than the Radeon HD 4870 X2.
Nvidia simply wants to win the performance crown back from R700. Adding GDDR5 memory and 55nm process will certainly speed things up and they will take the dissipation down.
Thermal dissipation is Nvidia's biggest problem as the chip turns to be extremely hot and the new 55nm should be a bit better. Once you take care of thermals, you can clock the chip higher which eventually means more performance.
The 55nm process with a new clock and GDDR5 memory should get GT200 55nm a bit faster than R700 and this is exactly what Nvidia needs.