NVIDIA has its secret weapon fully against RV770/RV770XT, apart from its GT200 lineup.
I really don't care about hypothetical "secret weapons".
As the previous high-end generation demonstrated, the fact that Nvidia's card had lower theoretical FLOPS figures than ATI's meant absolutely nothing in the real world.
The 8800 GTX "smoked" the HD2900 XT in every game, and the 8800 GT/8800 GTS 512MB "smoked" the HD3870 in almost every game too.
Based on most of leaked info from RV770 and GTX 280, i'd say the same will happen again this time. In fact, i think 2xRV770 might not even be enough, when you factor in the driver overhead and inherent inefficiency from Crossfire/SLI setups vs single card systems.