Games will not see a major benifit in the next generation of graphics technology.
Sure, there will be advancements that games can take advantage of. Most likely these will be dynamic tesselation and the unification of pixel and vertex shaders.
The real advancement for graphics technology will come in a different form this time around. We will see generalization of the GPU to the point of being used for generic stream processing, GPU multitasking/threading, and a major change in the way applications interface with this hardware.
Microsoft has discussed Direct3D's future movements towards "Windows Graphics Foundations" which will mean the GPU will become a common application resource used by multiple applications simultaniously. Widespread presence of PCI express will mean new possibilities in real time rendering, but it will mainly enable superior usage of available ram for graphical user interfaces.
Microsoft need to catch up to Apple and their Quartz rendering engine. Microsoft wants to do it better than them and will use DirectX development to drive ATI and nVidia development to enable superior looking desktop applications.