Cryptos haven't replaced the fiat yet and it won't in future too as many economies have declared it as an illegal tender. Without complete support and consistent flow cryto cant replace the fiat . Hope you got me! 
It is not yet even possible so soon. I think that it will take a lot of time, no doubt that even now in some place prefer to use bitcoin, but they are still using it as optional and not for everything they want. Therefore I think that it will take a lot of time when bitcoin will become so popular to use for everything instead of fiat currency.