2x increases are mostly limited to specific scenarios where newer GPUs excel, like AA, tessellation etc. On avarage the increases have been far more modest in the last few generations (after 8800GTX and 4870). That's why I expect a max 50% performance increase for next gen Radeon/GeForce on avarage. There might be some cases that produce 2x increase of course, but that doesn't mean that gen is 2x faster overall. 5870 more than doubled everything and resulted in ~70% performance increase on avarage. Based on the leaked specs 7970 is nowhere near double 6970, so even 50% increase would be impressive. The same goes for GK104. Of course architecture brings its own little spice. For AMD it probably results in a disproportionate performance increase in tessellation, perhaps even 2x in some cases, but otherwise perhaps lackluster general performance due to immature drivers. Nvidia has a more mature architecture so it'll probably have a more even performance increase.