Nvidia could easily come in with mid end cards faster than the stock gtx780/ti. They would just be clocked silly high and have no headroom. The review's would look good and they could price high as well. The reality would be once you overclocked the gtx780/ti they would be faster once more. Nvidia are great at marketing and i am sure they would sell.
Reminds me of the 480 vs 580. Similar performance but the 580 ran allot cooler.