We don't need to wait until the end of May to find out more about the upcoming Geforce 8800 Ultra card. Dell has actually leaked the 8800 Ultra specifications, but later removed the link. However, we were fast enough to capture the moment.
So, Dell confirmed the existence of the card and the specification clearly indicates that Nvidia is planning a 650 MHz card with 2160 MHz of GDDR3 memory on its odd 384 bit memory controller.
This is really a modest speed upgrade, as for example, EVGA already ships a 8800 GTX overclocked at 621 MHz core and 2000 MHz memory. With water cooling you can easily match 650 MHz core and 2160 MHz memory, or at least you should be able to.
The card still has 128 stream processors and it will be available with Dell's XPS 710 machines at later date.