The dollar is really the backbone of current world wide trade, there is only one way to destroy it. To cause world wide crisis. I don't believe that dollar's role can fade gradually, I believe that it can only be killed in huge crisis that we have never seen before. That is when we will see hyperinflation. Hyperinflation typically can only caused by geopolitical event. I have my gold with me and I'm prepared.....
Gold standard will return. Why? We need to ask why it ever exists. In a world with multiple competing super powers, the only money to trust is gold and silver. One super power is not going to trust the money printed from another super power. That is about it. As China becomes bigger and powerful every day, the world will no longer controlled by a single super power, and that is where gold will shine again.
There will be no global currency, we all know if euro ever worked. If it doesn't work so well in euro zoon, imagine to scale it to world scale.
There will be no world reserve crypto-currency, we all know how bitcoin ended.
The only fair play is gold and silver.