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?
I think cryptocurrency is acting now as one global currency but as of now, this currency is not intended for paying bills because people treat this as an asset to them which is they hold for a long-term and expecting to have a huge profit on this. Yes, a global currency but this is not like fiat that every people use to pay their bills.