More more number of and use of regression, unit tests by driver devs.
Go more piglit. This also counts for games that use OpenGL. Add some shader constructs rendering tests that you need to work in order to let your game work. This way driver devs can use tests and correct their bugs very early.
What I want to see:
Hyper-Z for r300 and 600, the r300 first.
Full OpenGL x.x(as much as possible) and everything required for WebGL and OpenGL ES.
(Through use of the es2 compatibility things, it only needs OpenGL2.x level hardware to do this decently right?)
Relatively bugfree r300-r600