R600 should start selling in May. At that time Nvidia will
come out with two new cards. We already mentioned one that might be called Geforce
8850GX2, a dual G80 card and you can read all about it here.
The second one as you can guess is the Geforce 8850GTX which is the faster clocked version of the G80 chip. We know it will end up clocked at faster speed than 600 MHz and that it will certainly make R600 run for its money.
We are not sure about the memory type but it might be even equipped with some high speed GDDR4 memory. We just know that Nvidia told its partner not to worry and that five month after the original G80 they have a real deal. It will be interesting to see how this turns out and we believe that Nvidia won't launch the new cards before ATI launches its R600.