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/2NeLgLrIn my own opinion, cryptocurrency can never replace fiat currency. Fiat currencies will continue to dominate as long as there are nation states and governments are powerful enough to enforce their laws. Fiat currencies exist because the alternatives, such a gold, ultimately failed to meet the demands of the modern world. Bitcoin is similar to gold, but actually worse in the supply is even more constrained.