EVGA has just released their 55nm GTX 260 212SP stock speed and SuperClocked variants. You can pick one up directly at EVGA.com. Widespread availability is expected to hit tomorrow morning.
In addition, Step-Up from a 65nm GTX 260 to the 55nm vanilla model is confirmed:
To anyone looking to purchase or Step-Up to one of these, here are my two cents. You might wanna wait a few weeks so NVIDIA can fine-tune its production of 55nm G200-103-B2
(GTX 260) chips and possibly leave you with a better binned card that has better overclocking potential? I don't know if this is true, but it's worth a shot.
Besides, NVIDIA is still trying to capitalize on the 65nm fabrication on all those consumers who don't care or know the difference. That can only mean that 55nm production will get better over time.
P.S. The B3 revision is the final revision for the GT206 chips.