I was watching CNBC last night and they said that there is concern that Iran will do one of three things:
Take a certain number of barrels of oil off the market
Cancle future contracts
Blockade the straights in the gulf doing military exercises to slow the flow of oil out.
They also had an analyst who has "sources in the Iranian government" and he was saying Iran's plan if they don't get their way will be to swarm our carriers in the Gulf with suicide boats like the USS Cole (only with many many boats this time), once they're sunk they'll blockade the gulf with mines and submarines. He said if that happens, $100+/barrel oil isn't all that unlikely.