Hawking radiation is almost certainly not going to win him a Nobel prize, because experimental detection is beyond our technology. But how about the singularity theorem which he and Roger Penrose proved? This theorem convinced the physics community that black hole would indeed form in realistic situations found in our universe when massive stars run out of fusion fuel. Unlike Hawking radiation, the existence of black holes itself does have observational evidence, which the Nobel Committee requires. Maybe awarding him a Noble prize for the singularity theorem is a possible way of acknowledging this legendary wheel-chair genius? On the downside, I guess some people would argue that proving the singularity theorem doesn't carry that much physical significance, since the concept of black holes had been around for a long time, and the only thing Hawking and Penrose achieved was to silence the sceptics.