Yes, I believe they will both work in concert although it is recommended to use two video cards with the same vRAM amount. However, a dual-GPU video card with 2GB will be every bit as good as two GTX460-1GB cards in SLI.
I sit here and read all these comments over and over and I wonder if you guys even know what your talking about. The new card is a Dual GPU card and YES, it can be run in SLI which would be like quad SLI but only TWO cards.
I used to run TWO ATI 3870 X2's in crossfire and a year ago a friend talked me into getting a GTX 470 Superclocked. Though I now have DX11 capability I lost Frames Per Second and can no longer play games Max'd out in the video settings. I never should have upgraded. Now I have to go out and buy another GTX 470 Superclocked and they are becoming hard to find at a good price.