For many years it seemed likely it would be the Euro. At least Russia and Iraq circa 2002/3 publicly threatened making the switch, there may have been others. However, it seems that Iran stopped trading oil in USD (as of 2012) and apparently now uses a variety of other currencies[0], although I haven't looked into this to see if it actually happened yet. I am under the impression that China currently buys oil from Iran in Yuan/Renminbi.

I'd be interested to know if Iran went ahead with its plan to stop accepting USD altogether. I'd personally be surprised if threats and posturing regarding Iran's nuclear program went away without some sort of agreement on USD oil trade.

If Iran has stuck to its plan to stop accepting USD for oil AND the US backs off I think that signals a pretty significant loss for the US not just in terms of its relationship with Iran but ultimately, in the long term, in its attempts to remain a dominant force in the global economy. It would be a result of pressure from an international community that the US government feels it needs to keep on side, but also conversely an international community that may have an interest in reducing the economic dominance of the US.

Your second question is an interesting one. I think the US' next move - or Iran's (potentially changing its mind about USD oil trade) - will tell us how strong the US is at this moment in time. The position of economic & military dominance the US currently enjoys (which helps its "intelligence" agencies to get away with actions that would be otherwise considered acts of war) is bound to end at some point. I'm not willing to stick my neck on the line and predict the end of US hegemony is nigh (I'm not really a crystal ball kind of person) but I'd just say that the signs of a superpower fighting for its position should be evident. There will come a point where the US can no longer risk such interventions.

EDIT:

Having read a bit more (though not much, to be honest, so I'm happy to be corrected) it seems the Oil Bourse is for oil-derived products not crude oil (it actually says this on the Wikipedia article, doh). Also part of the agreement that reduced sanctions on Iran was to stop taking gold as payment for oil[1]. So there's no need to worry about the US' position in the world just yet.

Anyway, hopefully in 2014 some members of OPEC will be seriously advocating trading oil in dogecoin ;). To the moon!

0: http://en.wikipedia.org/wiki/Iranian_oil_bourse 1: http://www.bloomberg.com/news/2013-11-24/iran-agrees-to-hist...

Euros or dinars, or anything that looks less of a ponzi scheme than the USD.

What will the CIA be able to do? What I said, overthrow their democratically elected leader, create terrorist groups, etc:

https://en.wikipedia.org/wiki/1953_Iranian_coup_d%27%C3%A9ta...

You might also have heard of Libya...?