http://www.beyond3d.com/#news10574
When looking at the performance element of NV4x, Jen-Hsun expects the performance increment from the previous generation to be dramatically higher than any previous architectural transition they have previously been through. Indeed, presumably speaking about NV40 specifically, NVIDIA?s CEO states that "if we?re not a lot more than 2 times faster I?m going to be very disappointed".
...
In the NV1x and NV2x generation more or less one two distinct processors were introduced and produced at the same time, with the NV3x architecture this increased to 3 processors, however Jen-Hsun made note that potentially as many as 5 distinct NV4x graphics processors may be in production at any one time.