Bernard Kerik is the person I hope GWB nominates for that post. I suspect Rudy could have it if he wanted it, but I suspect Rudy is going to remain a "free agent" so that he can run for either governor of NY or president. Asa Hutchinson, currently a deputy at HSD, wants the job. So if he doesn't get it, look for him to resign also.
I really liked Asa when he was an Impeachment Manager but think he's unhappy in his current slot; I think you're right that he'll resign if he doesn't receive the bump for this position.