McCain asked Admiral Mullen about it obliquely at a Senate Armed Services Committee hearing today:

MCCAIN: Is there any reasonable scenarios, Admiral—a prospect that trained Afghan security forces can handle the bulk of the fighting over the near to medium term?
MULLEN: No, sir.
MCCAIN: If we followed such a course do you think the situation in Afghanistan would improve or get worse?
MULLEN: I think it would probably continue to deteriorate.
MCCAIN: Thank you.