Bitcoin could replace, but the price of 1 single bitcoin would have to be maybe 200k dollars as the global economy is quite high compared to bitcoin value, anyway would be funny to see 0,001 worthing near 1 milion or more. But bitcoin at this stage cant replace the fiat, because the decentralization, a new bitcoin can be built controlled by all the countries.
Replacing will not happen. Of that I am certain. but I do think bitcoin could jump into the large gap for online payments. Be a competitor to paypal and expand it's horizon.
Because let's face it, fiat will be important, now and in the future.
I agree bitcoin will never replace fiat money, because of several grounds.
Government won't allow bitcoin to replace their national currency
Government don't want to be in economic crisis because of some bitcoin whale to dictate their economic course.
Government wont allow not to tax transaction and bitcoin technically nullify outside taxation.
and alot more.