Ati will probably release a higher clocked, perhaps DDRII R300 core for NV 30 debut or close, to spoil the party in good oldfashioned way, but I still doubt that there will be much of a difference, even though Nvidia will have 2 texture untis per pipe.
Reason being is that R300 is stretching all todays games to the max, so the difference will not be so great especially with newer/ faster R300. The diff will only be seen in 4xAA and aniso at 1280 + resolutins, as all the rest will be pretty much the same. And yes R300 will have pretty mature drivers by than, so that NV30 will need to be that engineering miracle Nvidia claims it will be.
However judging by CPU's that die shrink with process refinements, could push R300 speed for 1/3 rd I'd think so what would that make it.. 600mhz?
Woooot... but seeing this quite possible if they transition to .13 process and tweak the GPU a little more, as it is now in the bayb stage on .15 process and at 400 mhz.
I am pretty sure now that NV30 will be at least a 400 mhz part, perhaps even more?