No, I don't think he thinks they'll stop on their own, but I think he has a better idea of how much time he has to play with, than we do. (I hope)
Big problem here......just destroying their nuke plants isn't enough. They're hiding enriched uranium. Underground. Under Tehran, where 10's of millions of people live. (and under other cities). How do we get at it without risking 100's of thousands of people's lives? And are we sure we know the locations of all the underground stores? If we don't get it and just destroy the visible nuke plants, we don't know what kind of retaliation they'll take. The simplest solution is to get rid of the bad people....the regime. Nukes in the hands of people who are friends, won't matter much. (Guns don't kill, people Do.)
I'm certainly willing to go with a plan that gets rid of the Mullahs. It's a question of time, however. Once the Mullahs gain their nukes, then it will be very difficult to disloge them. As far as the underground facilities go, yes, you're right, they exist and will be difficult to destroy. However, the Israelis probably know where they are and using some bunker busters, we could set them back a number of years. That's the point. We may not completely terminate their program, but we'll push the date back enough to give us some breathing room.