Now the world currency is the US dollar. If I'm not mistaken, there have already been attempts to create a single world currency - bitcoin. But while it is still not so popular and predictable as the dollar.
US dollar will still dominate the world currency even their would be more attempts to try replacing it, as they already show the world how powerful they are and they really wanted to control in any aspect even the new President got a lots of criticism but still US will not allow any possible thing to happen to removes their dollar as the world well known currency.
Yes it is true, for the current USD still dominates the world economy, even in a variety of ways. His power is so strong everywhere. Maybe Bitcoin as digital currency a way to not be in the rule and power.