New Thirty Years War?

If the Saudi threat to back the Sunni insurgents if the US pulls out of Iraq are correct (and, on the face, they make a lot of sense), and given the general unease of Iraq's Sunni neighbors at the prospect of an Iranian dominated Shi'a Iraqi state, are we, as some think, on the verge of new Thirty Years War?

If we pull out, and the Saudis support the Sunnis, and Iran supports the Shi'a, how long before Saudi Arabia and Iran come to open warfare? How long before Jordan and/or Syria intervene? Egypt? This could be a nightmare quickly.

I'm NOT arguing that we shouldn't pull out, but the consequences are potentially devastating. And realists in the Administration should have realized this BEFORE the invasion, instead of daydreaming about candy and flowers and ponies for everyone.