Nvidia decided to cancel its NV48 project, and it seems likely that these cards will not appear at all. Originally slated to appear in Q1 2005, the cards have been dropped after Nvidia realised that it was a waste of time to push a 20 to 30 MHz faster card. Nvidia will make NV45 cards available to market to fill PCIe high end market, and that is the way it will stay until a new chip appears in the future sometime.
"NV40 and R420 chips will be known forever as the ones that companies pushed to their limits and Nvidia didn’t want to disappoint its customers with a marginally faster card. All it could manage was a 20-30MHz push, hardly anything to scream home about."