There are two things that can be said with reasonable certainty about Iran. First, the Iranian regime doesn’t enjoy the support of the majority of Iranians; second, the repressive elements of the regime are firmly united in their desire to wield power by both ideology and grubby self-interest. Dislodging the regime will, therefore, be extremely difficult.
The Supreme Leader will not live forever. The most likely outcome of his death will be a seamless transition to someone just as awful–just think of Cuba after Fidel. That is not a done deal, however. It is at least conceivable that there could be competing candidates for the job and that the regime could show some cracks that could be exploited by the opposition.
If it is ever going to happen, it will be then. Pressure from the West has not, and will not, result in regime change, but divisions at home might.