When we first went into Iraq, Afghanistan was thought to be "done". If we now divert forces out of Iraq, to Afghanistan, we may very well repeat the same mistake. Moving our forces around, thinking they were done, is part of the reason why the cost of the war is larger than initially expected.
I say we finish up Iraq on the planned time line and then put everything into Afghanistan. It would be nice if our "allies" could cough up some support, too.