Fiat is supported by the government and banks. I do not believe that cryptocurrencies are able to ever kill Fiat. But cryptocurrencies give people an alternative in their hands. Now banks and the government will have to compete with cryptocurrencies. If they unduly reduce the level of wages in the country, people will use cryptocurrency more. No need to starve or strike. Increasing the demand for labour will contribute to raising the level of wages.
That's the main difference between the so called crypto coins and fiat money; the later is currency and the former isn't!
A currency is supported by a central government, is regulated and paired with other currencies via institutional mechanisms.
No current crypto asset comes even close to the aforementioned definition, therefore it is incorrect to talk about "cryptocurrencies".
In our economic system fiat rules supreme because it is based on commodities like gold and oil.
The main role of crypto/blockchain technologies is to create an alternative way for people to makes transactions; faster, anonymous and without paying banks fees.
But replacing fiat will require a whole new world order and that's not around the corner...