I recall recently reading that the 260/280 have much increased registers in the chip, which gives me some speculation now, with the physx thing, that they may have been preparing for a chip meant to do both things at once and not lose "as much" fps.

I know it's too early to tell but I can sure see some games costing you fps just to go off and do your physx calcs. But the question will be how much, or on very high end chips, if at all? Still this thread is like kids in a candy shop and much fun to read.