It's codenamed RV670 and it's slated to arrive in the third quarter of this year.
Just as ATI introduced RV570 with 256 bit memory interface last year, this year brings the 256 bit DirectX 10 part codenamed RV670.
We don't have many details but we know that RV670 is going to be faster than RV630 mainstream part. The RV670 fits the performance market segment and it is the Shader model 4.0 DirectX 10 part.