Iran's internal structure is far different than Iraqs. We don't need to nation build Iran. We don't need to appease 3 different warring factions like in Iraq. Iran is fairly solid from my understanding so the chaotic political arena that occurred in Iraq, won't occur in Iran. Lets not forget that part of the reason Iraq turned chaotic was that Iran was funding insurgency against both the US and the Iraqis.
IMO here's whats gonna happen. (Just my opinion).
Back in 2017 I talked with some friends in the Defense industry. They work for companies that supply war planes and missiles. Two diff people, two diff companies. Both said the same thing. We're gearing up for late 2019/early 2020. They said that weapons manufacturing, aka missiles, were being ramped up to levels they had never seen before, even during the Iraq war. This tells me we're gonna be dropping hammers on a LOT of Iranian military installations. Our war simulations clearly show us we have no chance for a ground invasion. I also don't think theres any support for that in the public or in the military. This will, IMO, strictly be dropping bombs on targeted sites to set their military and nuclear program back decades. The only chance for "ground" action is through their proxies in Syria, Yemen, or Lebanon. I'm of the opinion that Iranian proxies are spread extremely thin right now so any actions against the proxies will be swift and force them to draw back.