
The reason for this is because ATI recently shipped the Radeon X800 GT and GTO cards and these can hardly co-exist with the RV530 (Radeon X1600). Additionally, ATI also has great volumes of both R430 and R480 chips and wants to use these to manufacture Radeon X800GTO and GT cards..
It this is true it will take until the end of this year before we'll be able to buy a mainstream Shader Model 3.0 card from ATI.