In order for bitcoin to replace fiat, it should be introduced by the government to their people, but if we are just going to wait for normal adoption, it will take forever, and some of us have already left bitcoin and new comers enters, so no increase in number, only in numbers of people who have experience using it, and that won't be good for bitcoin...
Just to be clear bitcoin will never replace fiat even if bitcoin is being used or almost used by everyone and I'm sure government will not introduce bitcoin in a way that it will be able to replace their own currency, sure bitcoin can become more popular than fiat but replacing fiat! no, it is impossible! but you know what is possible bitcoin being replaced by another digital currency created by a government!
If that was true, then the digital form of fiat (like what's seen on Paypal, etc.) should've already killed bitcoin. But it didn't, right? It's because people know that they're using cryptocurrency so they can be free from the chains that the government has put on them. It's the only way for us to avoid taxes.
You actually can't say for sure that bitcoin cannot replace fiat even though it can become more popular than fiat. Every single one of us (except those people in mountains, islands, etc) know fiat. So if bitcoin becomes more popular than fiat, then that's quite amazing because there would be people that knows bitcoin but don't know fiat. Like, how is that even possible?
PayPal is a company and the government doesn't have full control(not even sure if they have control over it) over it, what I was trying to say is if the Government created their own cryptocurrency it has the Possibility(understand the word possibility) of replacing bitcoin, it may not be worldwide but it is possible inside their country.
I think if they would issue such thing, it wouldn't replace bitcoins at all but would be a way for new people to enter the bitcoin world. At first, the average person would be glad to try out the cryptocurrency of their government. After being exposed to the crypto-world, they will see threads or articles about cryptocurrencies. And we all know that the mostly used cryptocurrency is bitcoin.
Ultimately, the government advertising a cryptocurrency of their own would lead to people using bitcoins and bitcoiners wouldn't be force to use the government's coin at all because they already know what they're doing.