Balance in the Middle East can be reached eventually IF:

Saudi Arabia alongside Israel and other Sunni Nations don't have an all out nuclear war sometime with Iran in the next 30 years or so and turn the whole middle east into a crater.

The balance would come when like in the past enough Shias and Sunnis kill each other and things settle down for awhile.

It's a little like the Hundred Years War in Europe between Catholics and Protestants. Shias and Sunnis haven't progressed past this stage of murdering each other yet.

Hopefully, this blood letting of thousands to millions eventually will be the last.