If the first tape out goes well the cards will likely arrive in September but if there are problems it could become November.
All we could confirm at this time is that the chip will be DirectX 10 compliant of course but it won't have the full implementation of Shader Model 4.0. It won't do the unified Shader but it will be Vista ready. Most of the chips out today are Vista ready at least the high end ones.
This chip has every chance to end up faster than ATI's upcoming R580+ fall refresh chip but this one will get R600 beast to compete with.