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?
Right now, US Dollar recognize as global fiat currency. Most commodities and world trade using US Dollar. Its already happen and i dont think crypto can replace US Dollar in near future because most central banks prefer using their own currency