I believe he has already stated his intent to continue some work on the project after GSoC ends, at a lesser rate. That was why he tried to get the complicated stuff done this summer and then later he can add in all the simple builtin functions that are missing like clamp, dot products, etc. that have to be done for all the different parameters types.Unfortunately, there's no word right now on future plans for the coming months -- if he will even be contributing to the Mesa project following the formal end of GSoC 2011 -- or eventual plans for graphics driver support and mainline integration.
Adding GPU support will likely be another major project. You'd need to write an LLVM backend to generate TGSI instructions, for a start. Not sure how much more work beyond that it would need.