Nvidia is making advancements to the GT200 line with the introduction of a 55nm GPU for the units. The fabbing of the part has now been confirmed after Nvidia made final preparations. Performance statistics should not change with the unit, but for any overclocker the process reduction will mean more room to play with.
I'd like to see the process reduction come with a reduction in price as well, since many GT200 units can still float north of or near $500 depending on what version you get. That makes them harder to justify, especially since AMD is back in the game with GPUs.