Though I am certainly no "fanboy," I think it will do good to have more of a selection, or at least a choice for dual-gpu cards for this generation of DX11 cards. AMD makes a fince Dual-GPU solution and it's upcoming will assuredly be an improvement. However with the lack of competition, there is no price war, and it is is better to compare apples to apples when benchmarking.
As many of you have pointed out the upcoming dual Fermi card will certainly be a downclocked cousin of the 580. If you go back generations of card from nVidia you will see this has been the case. The GTX295 was not a dual 285. It was a hybrid between that and the 260. Slower clocks than the 285 and the memory size and band width of the 260. It was such a good combination that nVidia split it in half and called it a 275. Go back one generation and look at the 9800gx2. Slower core and memory clocks. all the way around. And before that was the 7900gx2. Not a popular card but the story was similar.
Now imagine for a momnet this generation. If you look at some of the differences in the 580 vs 570 vs 560, you may be able to piece together a good speculation as to it's specifications.
512 cores @ 600-650 mhz
Shader clock 1400-1500 mhz
Perhaps only 1280mb ram with a 320 bit memory interface running at 3700-3800mhz
I certainly think it will have 2 eight pin connectors. And it lill be less than 800 dollars.
It's just my thoughts and I could be way off but it seems the logical conclusion.
Jason