That's what has been happening at the national level, and it's a significant risk at a regional or governorate level if you devolve power and power-share. They might have competing tribes within the Nineveh government, for instance, who don't power-share with each other within that governorate, and the problems are replicated at a lower level. It's a definite risk.
If good leaders emerge who convince people to vote beyond narrow sectarian interests, I think that's how, often, historically that risk has been overcome. There's no guarantee that will happen.