Um, it's not Petraeus' job to have a plan for Iran. His job is to manage the military affairs of the US in Iraq. No matter how badly he might want to put into action an "Iran Plan," his job is to report to his bosses that an Iran Plan might be needed. And then it is up to Mr. Gates, Mr, Cheney and Mr. Bush.
And what is their Iran Plan? Those with a memory recall neocons, in the immediate (and illusory) afterglow of Saddam's military melting into the population, harumphing that Baghdad was nice, but "real men want to go after Tehran."
It is obvious that Bush genuinely believes that the US would be best served by doing to Iran what we have done in Iraq. He and Cheney would even justify it to themselves with the notion that having learned such expensive lessons in Iraq, it only makes sense to amortize the cost of that education by putting it to immediate use.
Petraeus either knows or suspects this. The groundwork is being laid. After the Revolutionary Guard is declared a terrorist entity, Bush has legal grounds to attack Revolutionary Guard interests -- a de facto declaration of war with no Congressional supervision required. Yes, Congress at that point might convene impeachment hearings, but at that point it would be too late -- the die would be cast. It has never been Bush and Cheney's intentions to win a war in their 8 years. It has been to set America on a course from which it cannot turn back. And at that they have been masterful.
Explaining this doesn't mean I agree with it. But that is where we are heading.