Our shader compiler is getting better with every release. The performance increases from it will benefit all cards, including 9700's. Some upcoming updates will increase performance > 10% for longer shaders. For most of the current batch of applications, the shaders are pretty short already, so I don't know if they will get much benefit. We also have other optimizations that will benefit various cards in different ways (96's, X800's vs. 97's) -- I don't know most of them.
As for the X800 series, it's getting a lot of its upcoming performance benefits from our work in optimizing the memory controller. We've got a huge amount of flexibility in how it can be programmed and used, and we've just scratched the surface (the state space is huge, and it will take some time to come up with optimal cases). People can expect significant (>>10%) performance increases, esp for AA.