Looking forward to DirectX 11, which is surely a few years away yet, the Vole's stated high-end goals are to bring down the cost of authoring art for games, integrating with new PC hardware better, and enabling more interaction between the user and the game in the form of better physics, AI and other such gameplay functions.
To help with art costs - which are swiftly spiralling upwards, as games get bigger, longer and more detailed, thanks to next generation consoles - Microsoft will be implementing procedural content generation to help create larger textures. The API could also adjust image quality on the fly, within an engine - so if a game started to slow down as a level got more and more complex and busy, DirectX could scale back the detail level on screen to up the frame rate.
In terms of hardware integration, the XNA team pointed out that a number of hardware trends will need to be looked at. CPUs are adopting more and more parallel cores, and DX11+ will sport better support for parallel resource creation on threads, and a more friendly driver interface for working with parallel threading.