The SDR might become the reserve currency for the world but it will be a basket of major currencies like dollar, yen, yuan, euro and sterling. I think that for it to work they will have to revalue the price of gold by many multiples of the fiat currencies that make up the SDR basket. Basically the dollar is on its last legs as the reserve currency so the SDR will help spread the burden away from the dollar. Dollars, pounds and loonies will still circulate. The SDR will be the currency of account between sovereign governments only.