Chattering about demoting the dollar is one thing; finding a substitute world currency is another

It is one thing to want to replace the dollar, quite another to find a suitable substitute. The renminbi cannot be the chosen currency so long as it is pegged to the dollar, for its value will move with the dollar. The rouble is not a candidate, since there is not enough of the currency around to handle the volume of world trade and, besides, it is not the sort of money on which you can rely to hold its value, especially if oil prices collapse. Which brings us to the euro.
As has been pointed out by Jean Pisani-Ferry, director of the Brussels-based Bruegel think tank, and Adam Posen, a fellow at the Peterson Institute for International Economics in Washington: “There is no sign of a move to the euro as a global currency. The share of dollars in global reserves remains almost three times that of the euro.”