Sharing a currency takes trust. Countries like Russia, China, and India absolutely LOATHE one another and take every chance they can to 1-up each other or screw each other over on the bargaining table. The trust has never been there and I don't see how it can appear.

For such a currency to be an alternative to the dollar there simply isn't enough gold in existence, not at any sane price. Think about how many people would need to use it... More than half the world live in those countries! Maybe if the price of gold rises to $1m per ounce, there'd be enough to back that many bricbux but as soon as the price starts rising there would be supply shocks and other countries piling in, etc, and it'll simply be too hard for them to get the backing they need for all those backed notes.