I’m going to offer the rival prediction that if and when the Iranian government falls, there will be no mass conversion to Zoroastrianism [bold mine-DL], no widespread beheading of Christians, and Iran will…remain Muslim.
The point about Zoroastrianism is basically guaranteed, since Zoroastrianism today is unique among the ancient world religions that originated in the Near East in that its adherents actively discourage conversion. Also, it has not had any noticeable or significant presence in the land of its birth for many centuries. Quixotic attempts by the Pahlavis to consciously revive pre-Islamic Iranian traditions and names were, shall we say, not wildly popular, associated as they were with a rather brutal dictatorial regime. (For that matter, rampant Baha’i revivals are also unlikely, since the Baha’i faith hardly seized the imaginations of Iranians during the rule of the Pahlavis.)
This reminds me of two things that would be widely considered major drawbacks to the separationist plan. The first would be that an embargoed, isolated Islamic world (were such a thing possible) would almost certainly have a massive backlash against the native Christian populations, and the refugees we have seen fleeing Iraq for Syria would soon be fleeing the entire Levant for Cyprus and points west. The second would be that it would make Israel’s position totally untenable in the long term. No one would confuse me with an enthusiastic booster of the U.S.-Israel connection, to be sure, but the likely extinction of Judaism and Christianity in their native lands following the implementation of such a plan would be an unacceptable price for whatever “strategic goals” such an arrangement might serve.
Fundamentally, the hope of this plan is that Muslims will judge the merits of Islam based on earthly successes and failures. Though I cannot claim to know the minds of so many different kinds of Muslims throughout the world, my guess is that people raised up in a tradition that teaches them a theodicy in which trials and rewards are God’s will are not going to conclude that political tyranny or disastrous misrule are evidence that Islam needs to be fundamentally changed or abandoned all together. It didn’t happen for the entirety of Ottoman rule, and it isn’t likely to happen in the future. On the contrary, the woes of this world will make traditional Muslims all the more likely to turn to their deity for justice and mercy in direct proportion to the extent of the misery experienced.