Oil prices are falling, which cannot be good news for Iran (or Venezuela, or Russia, for that matter). Meanwhile, the European Union seems serious about punishing Iran for its failure to stop developing nuclear weapons. The just-concluded multi-lateral talks with Iran held in Moscow were a failure (as usual). Hence, the EU shut off of Iranian oil imports as of July 1.
Iran can still sell to China, of course, but even there the market is slowing. Oil is one of Iran's few foreign trade assets. Japan is the major country other than China that buys Iranian oil. We and the EU should have more influence with the Japanese than with the Chinese, surely.
As its oil sales decline, the Iranian economy will continue to ratchet downward. The question, of course, is whether public discontent and internal government dissent will happen faster in Iran than the development of its bomb. Another question is how much the continuing drop in government revenues in Iran will effect that country's several billion dollar a year subsidy of the Assad regime's army in Syria.