Pahlavi will not be in charge. The Iranian people are tired of the mullahs, but they don't want a fake either. The most likely scenario is a military led change, sidelining the religious elements, with a gradual move to plurality within context.
If he cuts some deal with the regime after an alleged massacre (and after he told the world he would take action if the Iranians killed protesters), Trump is just going full cartoonish super villain mode.