What will happen if we use a one currency only?

[winteroxalis]

Implementing a single currency worldwide would be highly impractical. Indeed, the prevailing theory is that a mixed approach is more desirable. In certain areas, such as Europe, gradually adopting a single currency may lead to considerable advantages. But for other areas, trying to force a single currency would likely do more harm than good.

[King Koy]

I don't think that will happen, in order to do that one person or government must conquer the whole world which is very impossible because it will be the great defeat ta a one person or a nation if he will attempt to make a war against the world.