I think bitcoin will be partly decentralized, partly regulated in future. Only this combination will allow it to compete with other world fiat currencies.
Yes it could have happened, bitcoin possibly also can master the world currencies but still in the digital world, because every country has its own characteristics of their currencies. and more developed own bitcoin and known by the public in a network the internet. and this will be increasingly bitcoin is often used to Transact due to more efficient and save time.