Still, I think it is not enough to replace the fiat currency. It will be hard for the government to do that.
Who said anything about asking the government's permission? The whole point of bitcoin is to move away from giving other people control over your money.
Well, can you tell us how you will use cryptocurrency if one day the government of your country will introduce criminal penalties for its use, start blocking all exchanges and websites and restrict merchants from it use? If you think that there are no ways to block cryptocurrencies, then you are very much mistaken. Why don't they do it? Because politicians have not yet fully understood whether they need cryptocurrencies or not.
If they come to the conclusion that it is necessary to completely close crypto story then neither Satoshi nor Buterin nor anyone else will be able to influence this. To believe in the total impossibility of banning and blocking something is not very smart, as for me. Yes, they cant fully stop the network but they can dump it and make mostly useless