Speculation at theinquirer says the following:
My question is: Is R520 prepared for SM4?
Edit: http://www.theinquirer.net/?article=25937
AT SOME POINT Microsoft will release a new DirectX upgrade. We didn't expect that DirectX 9 would get some significant upgrades before Longhorn/Vista, but it sounds like the Vole changed its mind.
The company told this to a bunch of developers back at the Game Developer conference in London last week, and this meant that next generation Nvidia and next generation ATI R600 parts will be ready to show their feature sets even before Longhorn comes out to play.
It's a great decision as both Nvidia and ATI Shader Model 4.0 parts are expected sometimes toward the middle of 2006, before Longhorn arrives. We don't have any idea what it is going to be called but DirectX 9.something sounds like a reasonable guess.
If Microsoft decided to wait for the Longhorn for those new shaders, this would have meant that the next generation Nvidia and ATI chips would have had to wait for a few quarters before they would be able to get the full Shader Model 4.0 functionality.
The move from Windows XP to Longhorn will take years and Microsoft knows it, and I can bet that big games publishers would be veru upset if Shader Model 4.0 was a Longhorn baby only
My question is: Is R520 prepared for SM4?
Edit: http://www.theinquirer.net/?article=25937