Well, I have too little data to make aprofessional estimate. But if you want a SWAG, here's what I think would happen.

The Northern Kurdish region would stabilize with occasional hiccups caused by the Turkish Kurdistan movement.

The main power centers of Baghdad, Basra, etc. woud split into warring faction -- not just Shiite v Sunni, but also tribal groups seeking fame and honor and dominance and revenge.

The central government would have two choices. One would be to unite all the armed elements into a strong army which dramatically suppressed violence, insurgence, and even disagreement.

The other would be to fall apart and give way to tooth and claw evolution -- after a century or so of ongoing bullshit, some form will evolve that will stabilize the region. A strong leader, a monarch or dictator, would emerge if allowed to. OR the individuals of Iraq will find their own voices and stand up for mutual aid and common consent and a democratic gnostic republic.

A