John showed a whiteboard drawing of what's left to do for the open-source OpenCL support using Gallium3D Clover with modern Radeon HD graphics cards using the R600g driver. About 108 weeks it looks like, assuming no other developers contribute. On AMD's side they have Tom Stellard working on the GPGPU support and Alex Deucher to also help. However, they haven't updated this drawing since looking at the progress made on the OpenCL state tracker this summer via Google's Summer of Code.
Below is the drawing with rough estimates (numbers represent weeks for completion). Items scribbled out are future Radeon GPUs (e.g. Southern Islands, etc). Hopefully John Bridgman will be able to post a better image of this drawing in the Phoronix Forums.
With PathScale already having an OpenCL run-time and a compute abstraction layer working for their PSCNV driver (their Nouveau driver fork) and this being portable to Nouveau, the open-source NVIDIA Linux driver may be the first one to bring-up OpenCL support for Gallium3D drivers.