Iran scenarios

Scenario A: Iran succeeds in building a nuke while tying up US in Iraq.

Iran wants this nuke because historically the US has negotiated in an entirely different way with nuclear powers (to whit India, Pakistan, PRC (mainland China), and N. Korea all are treated quit differently than they were before they had nukes). Eisenhower's administration actually discussed nuking the PRC during the Korean war but Eisenhower (bless him), would have none of it. After the PRC had nukes somehow the option was tabled.

In my opinion, the talks with N. Korea only happen because the N. Koreans have nukes. Before the nuke the only card the N. Koreans had were thousands of heavily fortified artillery within range of S. Korea's capital Seoul and a large fraction of the S. Korean population (if the "balloon went up then you could kiss Seoul good bye).

With this nuke the EXISTING theocracy can treat with the US from a position of power. The result would be an end to the embargo, a better economy, and continued theocratic, anti-democratic, control for another generation at least. The Iranians would also have domestic nuclear power for when their oil runs out.

Scenario B: Iran's oil runs out and they have no economy to speak of as they are still under embargo.

The population is furious with the existing theocracy and radicalized enough to embrace any exit. The result is a less-than-velvet revolution with a dictatorship much like Pakistan. My guess is some young officer in the military would probably overthrow the Mullahs.

Scenario C: Iran's ruling class somehow realizes that they care more about their kids than their religion.

The mullahs, under broad social pressure and with the encouragement of the military, yields increasingly more power to the EXISTING elected government. This transition is acknowledge by the West and the embargo drops. Increased world trade brings Iran closer to the world economy much like the PRC has learned to love the Western cash-flow.