He does seem to be aware of the challenge and is working on it here
Aside from that, one of the folks who was helping with RE (Phire) before the documentation was released is playing around with driving the pipeline https://github.com/phire/hackdriver
. However, the aim there isn't to write a proper driver.
Then there's 'clever' who has taken hackdriver and modified it to display the output on the screen and spin the triangle. He has also worked on getting around some of the security issues of poking memory and using the mailbox interface directly. He has put up a video here:
From what I gather, the current plan is to write up some design docs and have people who are familiar with the Linux kernel, Mesa/Gallium and the right way of doing things look over them to make sure everything is sensible and then start working on a proper driver from scratch.
Finally, there are the razdroid guys who are currently working on porting the driver as well.
For those interested, the relevant IRC channels are #raspberrypi-internals and #razdroid on Freenode.