There will be no consequence for Saudi Arabia disintegrating. Most of the world (hint: their neighbors and their own population) will welcome it. S.A. has lots of lands and other resources (religious tourism is big, they are the center of the Islamic world). They are only poor because of their own mismanagement.

The Emirates will be largely fine since they have diversified a lot. They might need to cut a bit of spending but otherwise they'll keep as a wealthy nation. Qatar will also probably be fine. They have lots of money and built lots of infrastructure which they can open to the world.

Actually, I think post-oil, we'll finally have peace in the region. Nothing to fight over any more.