If a new desktop architecture weren't imminent I'd say the GPU division would be the clear favorite. But AMD brought in (and brought back) enough talent over the past year or so to work on next-gen x86 that I wouldn't want that talent to be lost.
Though you do have to wonder how much more competitive AMD would be against nVidia were they to throw all of their x86 R&D at GPU... Because the main worry is that, next-gen arch. or not, AMD doesn't currently have the resources to compete against Intel and nVidia simultaneously for long.