The world has one global currency, I think it's impossible. To make everyone have the same thought is impossible, and surely there will always be those who oppose or support, and it will be difficult to make one global currency.
In my thoughts as well in the whole world having only one currency is not very easy, each country has their own currency, but to be honest I really want that we could see bitcoin only currency as global currency, because it will make the countries closer to each other in world there will be great peace, we lets hope for the best as we only can try and pray to have these changes in our surroundings.