NVIDIA's next-gen family 28nm GPUs, code name 'Kepler', are expected to come a little later than AMD's 'Southern Islands', however some numbers have been compiled to whet your appetite. The GK104 appears to be targeting AMD's 'Tahiti', with a 384bit wide GDDR5 memory bus over PCI-E 3.0 interface, however the GK 104 is not set to be the flagship part. The GK100 will be the GPU to reign over the Kepler family and will show that NVIDIA mean business.
est 1024 CUDA cores
est 128 textures units
est 64 ROPs
est 512-bit GDDR5 memory interface
As you can see, they are stated to be an estimate but in consideration than the GPU fab has missed out 32nm and went straight to 28nm, doubling up core count would almost be rude not to and while we cant be sure of actual performance I wouldn't hesitate to suggest near GTX590 level. Launch is expected in Q2 2012.
640-768 CUDA cores
80-96 textures units
256 to 384 bit memory bus
The GK104 performance is rumoured to be better than a GTX580 with well over 2TFLOPs of compute performance and is expected mid Q1 2012.
While of course none of this is official, thus I would heed caution, it does give a realistic impression of what to expect. The AMD 7000 series is expected to launch around CES 2012 so it would not be surprising if informants were allowed to leak snippets of information to encourage some to wait for the green party to arrive with the 28nm GPUs.