Could you see a future wherein the entire world shares one global currency, be it fiat or crypto? If I think it in a scifi kind of way, it would most probably be some digital currency that could all just use. It doesn't even have to be in this century. Maybe the next?
US Dollar already be global currency and its controlled by The Fed. I think its hard for cryptocurrency even for bitcoin to replace dollar domination in global transaction. Central banks wont lose control on money supply but i am optimistic that bitcoin or others cryptocurrency will be used for payment in near future