Our pal TV reporter (and late night authority) Aaron Barnhart addresses the question of who's the current King of Late Night. His answer is my answer: No one.
I suspect there's very little chance, as Aaron speculates, of Letterman retiring soon. I also suspect that Craig Ferguson would only get a shot at the time slot if an awful lot of other folks turned it down or proved to be unavailable. But I also can't tell you who the front-runner would be.