GTX 460 was Nvidia's life saver, and all reports are indicating that it has been selling well. Even AMD admitted that to its analists. This is the main reason why Nvidia won’t release a new GTX 560 until early next year. This is the card that is supposed to replace the GTX 460.
The new card is based on GF114 chip, which is an improved GF104 with better clocks and all eight clusters enabled. If you enable all eight clusters the number of shaders jumps from current 336 to 384. The math behind is very simple. “Each Streaming Multiprocessor(SM) in the GPU of GF104/106/108 architecture contains 48 SPs and 8 SFUs Special Function Unit” more here
Also the complete GF104 core contains 64 texture address units and 512 texture filtering units.The number of SFUs jumps from 56 to 64. You can also expect a significant increase in clock speed as well as memory and the “new” card will run at higher than 675MHz core and 1350MHz shaders.
The launch of the card is a sales decision and it will come only if Radeon HD 6870 and 6850 see dramatic price cuts and put additional pressure on Nvidia. If all goes as planned you will see this card early next year.
We expect some average 15 to 20 percent performance increase from GTX 560 compared to GTX 460.
Of course GF104 had all these clusters inside but Nvidia has simply dissabled one as it didn't need so much performance back at the summer time.