According to documents seen by Fudzilla Nvidia will certainly not launch any new high end card by the end of the year. It is about to launch the D8P, a performance card in the $199 to $249 market and a D8M which ends up to be G98, an entry level card. There won't be any new high end chip at least not this year.
Geforce 8800 GTX and Ultra will remain the fastest cards from Nvidia and whoever bought a 8800 GTX really got a lot of gaming performance for his money as it can still claim the performance crown, almost a year after its introduction.
Nvidia's next high end card comes in 2008 but we still don't know when exactly. Last time we heard about it it was scheduled for Q1 and our sources talked about double PCB GX2 like card.