An of engineers from Saarland University in Germany publicly said that G80 has 160 stream processors. He said this at their CeBIT presentation. The rest of the world knows that the G80 is supposed to have 128 only.
We believe that these hardware enthusiasts with PhD's know what they are talking about, and there is a strong belief that Nvidia actually enabled 128 streaming processors only and is keeping the rest of them for a later date.
All this can be done in the driver, as you can enable as much stream processors as you like and you can enable the rest when the time is right, e.g. when ATI releases its R600 chip. We will try to find more about it, but we think we are on a fine lead. It would be cool if he is right, for maybe he has pre-announced Nvidia's next chip.
Time will tell, and we heard him talking about it when we saw the presentation here.