It's true, they are sitting atop massive oil deposits, but it's also 80% of their economy. Restructuring an economy and energy policy takes a lot of time under normal circumstances. Just look at Brazil it took them nearly half a century. If the UN sanctions were repealed today it would take a couple decades for the damage to be undone. So in reality it would take them at least two generations to restructure so growth can begin. They've already made ~30 years of progress towards restructuring the energy policy.
U.S., allies conduct 31 air strikes in Syria and Iraq against ISIS militants (Reuters)
from the article: U.S. warns Iran: Meet nuclear obligations or face 'next step'