The way it should end up is Corum will eventually settle in as the early down option. He is better suited to take the beating. KW change of pace and/or when Corum's carry count needs management in the game.
Basic goal here is to keep KW fresh for the playoffs. With Corum you have a guy who should represent little dropoff. This means they are going to use him for that purpose. Also when it comes to third downs, I think KW is the better option. So this means his carries and usage should slant towards that end of things.
Only thing that derails this would be one of them getting hurt. But barring injury that's the way it's heading IMO.