But the regime of the ayatollahs in Iran grew out of a secret society called the Devotees of Islam (فدائیان اسلام), a Muslim Brotherhood affiliate whose founder and leader in the 1950s, Sayyid Navab Safavi, was a close associate of Ruhollah Mostafavi Musavi Khomeini. 
Khomeini, Navab Safavi and the flag of the Devotees, فدائیان اسلام
Their flag is a direct allusion to the symbol of the last Ottoman Caliphate [see first picture of this post].
Navab Safavi founded the Devotees of Islam in 1946 under the impulse of the Muslim Brotherhood.
So I think Iran will ally with the Muslim Brotherhood in order to reinstate the Caliphate.
Look at Qaradawi: their organization is oecumenical, it goes beyond the Shiite/Sunni faultine.
Ruhollah Mostafavi Musavi Khomeini, young and old.