I wouldn’t be so sure that this is what we want to happen. Governments receive partial control and, much more importantly, a source of money from the current fiat system. In turn, they provide services, care about welfare and safety inside the country, etc. I assume you’d expect them to continue doing that, right? But if we totally switched to cryptocurrencies the taxation would be so much complicated. How to ensure that everyone pays taxes if everyone tries to stay anonymous?
I don’t know, maybe it is possible to regulate somehow, maybe it will be so in the future. But the important question is: do we really need it? I think fiat and cryptocurrencies can coexist just fine, benefiting both governments and people.
Nations do not get a source of money from fiat to do stuff, I mean they shouldn't at least, printing money to do what a government has to do is not the right way. What they should do is tax people and get that money and use that money to help everyone, some stuff are not charged in this world, you do not pay the firefighters that stops the fire at your house right? So, some stuff needs to be paid by government and they should use that from the taxes.
Obviously speaking we are talking about many nations coming short and using that money very inefficiently, nations that could send 1 rocket to space for exploration every single day with the type of tax they get end up not even fixing the roads is the norm we are used to these days, this has nothing to do with your ideology or politician you like, EVERY one of them are like that in this day and age. So bitcoin or fiat, nothing will honestly change if you ask me, because it is the people at the top that is screwing us over, no matter which currency.