What will happen is this:
Late 2012 - as sanctions and oil boycotting of Iran begin to bite, Iran will agree to, or propose, weapons inspections by the UN.
Mid 2013 - weapons inspectors report no evidence of Iran having a nuclear weapons or any other WMD programme.
Mid/Late 2013 - west presents evidence of what it believes in Iran impeding weapons inspections.
Late 2013/early 2014 - Iran suspends weapons inspections indefinetely.
Mid 2014 - build up of western forces in middle east (exempt UK - who will be trying to reinforce Falklands to protect its on own oil interests there.....)
Late 2014 - west invades Iran. Short conflict of maybe 6 months, until regime overthrown and temporary government put in place. A lengthy insurgency follows with 10,000s civilians killed, 1,000s of US/Allied servicemen/women killed.
Mid 2016 - first free elections held in Iran.
2022 - US withdraws last forces from Iran. No nuclear weapons or other WMD ever found in Iran.
If I was President Ahneedadinnerjacket I would be trumpeting the West's WMD record on Iraq right now. I would cease all oil exports to the EU and North America. Then put in place a 20 year agreement with China/North Korea/Russia to sell them vast amounts of oil and below market prices.