It seems that ATI is releasing their 6 month refresh this May in the form of the Radeon HD4850 and HD4870. Some sites already have specs and all for them.
The HD4870 sports 480 stream processors, 32 Texture Units (sucks) and 1024MB of GDDR5 3.8 Ghz memory (yay) on a 256 bit bus width (bleh). Their texel fillrate performance is... well, comparable to the likes of the 9600GT, but again, this are not supposed to compete with the higher end GeForce 9s. The HD3870 is supposed to retail for $350USD.
EDIT: I forgot, these are based on the RV770 core. Plus the shader clock is now unlocked from the core clock.