According to some of Nvidia's partners, on April 17, 2007, the GeForce 8800 Ultra will be launched together with the GeForce 8600, GeForce 8500, GeForce 8400 and GeForce 8300. GeForce 8800 Ultra will really be Nvidia's response to ATI R600, however the specifications of the new cards haven't been revealed yet. Most sources, however, believe that GeForce 8800 Ultra will run at higher clock speed than GeForce 8800 GTX and may feature GDDR-4 instead of GDDR-3 memory onboard with the corresponding frequency increase. However, even today Foxconn Company is already offering an overclocked GeForce 8800 GTX with GDDR-3 memory working at 2100MHz frequency.
News source: Xbit Laboratories