Even though they may lose their dominance over oil/gas...the Moslems have been very smart to start using Sharia Banking as a holding ground element...it might not be as lucrative as oil - but it could sustain these evil empires and allow them to survive and continue their jihad into Western nations...
Sharia investing is a potent a form of economic manipulation similar to the oil cartel idea but it is not as easily controllable as the spigot emanating from the ground in country. Oil is still king of the roost in terms of political power and the power it gives to the House of Saud in terms of their ability to maintain power in the Arabian peninsula.