I suppose if both Cena and Orton are indeed gone, Sheamus would be the next most popular face? A champion vs. champion match could be fun. It would play into Punk's best in the world complex, might help elevate the WHC a bit, and could really freshen up both title scenes depending on how much of a risk Creative is willing to take on it. Also throws in Ziggler's cash-in as a possible wildcard, too.
So of course it'll never happen.