Do you think it will ever replace fiat currencies then?
I think it eventually will. Silver replaced gold, then IOU backed gold pieces of paper replaced silver, then the value of the state's IOUs replaced gold, why not bitcoin replace IOU's that aren't backed by anything?
Because those IOU's are legal tender and every economic system needs a legal tender.
It's not true that they aren't backed by anything. They are backed by the law.
The role of cryptocurrencies is not to replace the legal tenders, it's to add further options to them.
In order for Bitcoin to replace the legal tenders, you need a law - a constitutional law - declaring Bitcoin legal tender.
I don't think that's going to happen.
(Frankly, I even don't want that to happen. I want each country having its national currency, as part of their national identity.)
Besides, no business is going to accept as payment currencies that a month later could lose 30% of its value.
That would make every financial planning impossible. So, that business should convert their Bitcoins into another, more stable currency.
Before talking about Bitcoin as a potential currency you have to explain how to solve the volatility problem.