The USD is heading south like any other fiat currency on this planet.
More and more are trading with each other without using the green paper.They are ditchind the USD in foreign trading.
Also petrodollar is becoming less and less relevant.
Some older articles I've found quickly.
http://www.huffingtonpost.com/alastair-crooke/petrodollar-us-saudi-policy_b_6245914.html
http://www.forbes.com/sites/energysource/2014/05/29/the-colder-war-and-the-end-of-the-petrodollar/
http://www.zerohedge.com/news/2015-01-14/russia-just-pulled-itself-out-petrodollar
This however doesn't mean the USD will disappear the next decades.
But Bitcoin will hopefully be well known and used beside this shitty paper.