Islam is entirely predictable. Hearken back to the golden age, the prophet and his companions, one true way, war against unbelievers and so on.
What will save Iran is a combination of three things. First is the youth, as you mentioned. Although we are getting a somewhat mixed picture here, as the youth we see on the internet and interact with are inherently going to be those attracted to the west. There are many just as many who volunteer for IRGC and Basij, that lay into protestors with batons and attack areas where homosexuals congregate.
The second factor is the issue of clerical leadership in Iran. It may seem like this decided thing to those in the west, but it is not. Vilyatefatiq (guidance of the elders, or something like that. My Farsi is rusty) is not univerally accepted by the elders (the clerical class). There was a very real question of if Khomeini was the only one fit to the supreme leader. And each subsequent supreme leader, each one removed from 1979 by the years, is going to have less of that Khomeini magic to channel.
Third is the internal make up and inherent stability of Iran. Name the last time Iran attacked another foreign power. It’s been a really long time (I’m talking about full on war, not terrorism by proxies). And internally, Iran is more of an empire than it is a nation state. You’ve got Fars, Turks, Kurds, Balochs, Bakhtari, Turkmen, Lurs, Arabs and a few more I’m forgetting. The moment the government in Tehran takes its eye off of the ball — internal security — you’re going to have an eruption of ethnic violence that will be hard to stop. Just because it hasn’t happened does not mean it cannot happen.