GK104 is a 256-bit upper-mid-range Kepler part though. It shouldn't technically beat HD7970 based on its ranking in the NV hierarchy. Basically if you take away the branding (they can call it GTX780 for all we care, etc.), this card is a direct replacement of a GTX560Ti as I have understood it. All NVidia really needs to do is launch it at $399 with performance between HD7950 and HD7970.
I can't see GK104 having any chance outperforming an HD7970 in overclocked vs. overclocked states considering it's supposedly a 256-bit card and given the immense overclocking headroom that HD7970 has.
Your comment about it performing similarly to HD7970 given the die size? I am not sure: 256-bit vs. 384-bit. Also, NV likely has extra transistors allocated for things needed in Quadro, Tesla markets, PhysX. It's hard to imagine an NV chip being more efficient per die size.
If
hypothetically this upper-mid-range card can actually beat HD7970 in DX11 games such as Batman, Crysis 2, BF3, Metro 2033, I don't know how NV can price it at $450+, since in the end it's still their mid-range card . . . unless the new mid-range is going to become $400-450 battleground?