This is where the BRIC thesis for a new global currency based on the IMF's Special Drawing Rights breaks down. The SDR is backed by the reserve of gold it keeps, thus making gold still to be the ultimate universal currency, so even the IMF is bound by finite limitaions. Loaning to an ever growing need in more countries while still simultaneously maintaining a global standard for SDRs as a Central Banking currency worldwide, is not realistically feasable at the cost of selling large protions of its gold holdings at one time. Even if this is measured over a period of a few years, the outstanding loans are issued for longer periods of time, so the sold gold cannot be rotated back into the IMF's coffers as quickly with other repaid loans. The American dollar will remain for some time to come as the principle global currency despite whatever global economic fortunes come with it.