I heard this from this asian conspiracy theorist from many years ago like 2011, he said in the future there WILL be a one universal currency. Which he meant every where in the world will use that currency and other currencies will disappear. But this universal currency where will it come from? bitcoin or from the fed? I think in the future there will be 2 true currencies, that 1 is the bitcoin and the other will be from the fed. Only time will tell.
no one will know about this, but i don't think this will happen in short term because there are too many complicated thing that is happen in all country and they need to fix and solve the problem first. then after this, maybe they can try to use bitcoin as alternative currency for their country and see what their citizen opinion. if the citizen is satisfy with this, then the government will continue to improve to make better with both currency but if not, they can disable one of the currency.