No never, this can never happened because bitcoin is not created as a competitor to fiat rather as a supporter to help facilitate transactions, I don't think anything in this world could over take financial system as i know this system has been existing for decades nothing has ever taken its place till date. Not even bitcoin could take it's place, bitcoin is create to relief mankind from stress of going through hard payment system by staying at home and make a quick transfer without the need visiting banks if your funds are already in digital currencies.