The European Parliaments Committee on Economic and Monetary Affairs (ECON) has come up with a report on cryptocurrency entitled Virtual currencies and central banks monetary policy: challenges ahead. The finding of reports shows that cryptocurrency will not replace fiat currency, even in the long term.
https://bit.ly/2NeLgLrAs far I know, bitcoin created not for replacing fiat money. Bitcoin created system to disrupt banking system. Fiat currency must be still exist in next few years because for some peoples its more convenience and more flexible.
But i am believe in many years to comes, peoples will using bitcoin for their transaction because its more safe and its peer to peer transaction