Ron Paul said:
"The chaos that one day will ensue from our 35-year experiment with worldwide fiat money will require a return to money of real value. We will know that day is approaching when oil-producing countries demand gold, or its equivalent, for their oil rather than dollars or euros. The sooner the better." (emphasis mine)
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The geopolitical sands of the Middle East have been rapidly shifting.
The faltering strategic regional position of Saudi Arabia, the rise of Iran (which is notably not part of the petrodollar system), failed US interventions, and the emergence of the BRICS countries providing potential future alternative economic/security arrangements all affect the sustainability of the petrodollar system.
In particular, you should watch the relationship between the US and Saudi Arabia, which has been deteriorating.
The Saudis are furious at what they perceive to be the US not holding up its part of the petrodollar deal. They believe that as part of the US commitment to keep the region safe for the monarchy, the US should have attacked their regional rivals, Syria and Iran, by now.
This would suggest that they may feel that they are no longer obliged to uphold their part of the deal, namely selling their oil only in US dollars.
The Saudis have even gone so far as to suggest a "major shift" is underway in their relations with the US. To date, though, they have yet to match actions to their words, which suggests it may just be a temper tantrum or a bluff. In any case, it is truly unprecedented language and merits further watching.
A turning point may really be reached when you start hearing US officials expounding on the need to transform the monarchy in Saudi Arabia into a "democracy." But don't count on that happening as long as their oil is flowing only for US dollars.
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