So what can we expect:
* a ground invasion is pretty much out of the question considering the geography or Iran and its neighboring countries.
* Iran destroys every oil production and transport sites in the region (say good by to your election, Republican Party)
* they could fast produce the bomb and test it underground as a final warning
* OR they fail and resort to more desperate measure like a dirty bomb
* OR they fail and there is some sort of regime change
* Or there is some kind of extended war of attrition and it makes the refugee crisis from the past 20 years seem like it was a mere tourist wave.
In any case, this will accentuate the Qaddafi effect and more nations will follow the North Korea option of nuclear "unauthorized" nuclear dissuasion, which is also the case for Israel by the way. Talking of which, Israel will become politically radioactive in the world. Its support is already negative in nearly all countries and has dropped significantly in the US such as the evangelicals.