Actually, since Iran launching a nuke at a heavily populated area (say, bigger casualty figures 'achieved' than hiroshima) would mean pretty much the end of the world for human civilization, I don't think it's unreasonable for Iran to launch an intercontinental nuke. Think, for example, if all the social welfare programs that they offer are no longer relevant (bad example actually, they probably don't have much in the way of such programs in Iran). Then they could pour all that funding into getting a nuke. I mean, what the hay, they could even just steal one using an agent inside a country that does have one.
Anyway, it may be useful to note that it would be pretty easy, in comparison, for Iran to threaten Israel with a short-range one. It's in their freakin' constitution. That may actually be better for the world - maybe Israel would be able to defuse the situation more or less by itself without anyone getting nuked.
Damn. And I thought I was going to live long enough to get my PhD.