Much noise and doubt from the EU and UN remains to sort through about Iran and its apocalyptic aggression; however the leading indicator I am told to watch, at the end of the day, is the US Navy.
When it is time, the POTUS, whoever he is at the time, will deploy multiple carrier battle groups to the Arabian Sea, Persian Gulf, Med, Indian Ocean; and the deployment will be deliberate and over weeks. The interval will be a form of last grasp diplomacy.
Until the fleet puts to sea with the usual arsenal of recon and strike aircraft, until the straegic bombers concentrate, the posturing in Tehran and Vienna and Washington will be entertainment value only. Enjoy.