Production cards in volumes are expected some two weeks after the sample phase and so they'll be available to buy in the last week or August.
The second wave, powered with RV560 and RV570, the new Radeon X1900 GTO is expected in September time, and the cards should be out by the end of the month. We can bet that Nvidia is also preparing a refresh of its cards but we still don't know what is set to replace G73 and the like cards. We are anxious to see the G80 in action. µ