Nvidia is rumored to be rushing out (February is the word on the street) a high-end card featuring the Kepler 104 GPU in order to compete with the recently released HD 7970. So far this mysterious card is said to have 2GB of GGDR5, a clock speed of 780Mhz, a 225W TDP, and (only) a 256-bit memory bus.
A 256-bit memory bus seems a little weird to me. Nvidia has used a 384-bit bus on their GTX 480 and 580, and a 320-bit bus for their GTX 470 and 570. The 256-bit cards have all been strictly mid-range parts in the last two series.
The Kepler 104 is supposed to be competitive with the HD 7970, but the sources are saying that it is not the highest-end GPU being developed by the green team. The real new flagship is said to be the Kepler 110, which will be released sometime in March or April.