Seems to me we are close now to the Kurds being forced to make the big decision.
They will very soon have to decide whether they really want to retain the protection of the US and head steadily towards becoming the only remaining relatively safe place for Americans in Iraq, and a very small, oil-rich state surrounded by very interested enemies, or deciding that their future is not guaranteed by a failing state like the US and that they need to become full members in good standing of the new Iraq, whatever that might be.
If that happens, how long will it be before the Kurds say to Bush, "thanks for the last 12 years, but your alliance is now a danger and a liability to our long term survival. We are joining our Sunni brothers and their new Shia allies and asking you to go. If you choose to remain against our wishes, all bets are off."
I think we will see that happen in the next couple of weeks if the violence continues, and by handover date in any case.