The only way fiat is going to die is when the population will lose faith in it and the government will fail. Even hyperinflation like the one currently happening in Venezuela is not enough to kill fiat, many other countries have had it at some point of their history, and they've usually solved it by rebooting their currency. Too many people are dependent on it - people employed by the government, people who pay taxes and so on. I don't believe in Bitcoin revolution, Bitcoin will just keep coexisting with fiat and will have a relatively small userbase consisting of people who value its properties.
I'm also quite skeptical that Bitcoin is going replace fiat currencies, unless people abolish governments entirely. Governments have no incentive to give up monetary control, and they will continue forcing people to accept legal tender for payment of debts and taxes. Most people are passive sheep and will do what government and society tells them to do.
The path I see is one where BTC gains status as a traditional investment asset. Governments and central banks will be forced to hold reserves as a hedge against geopolitical risk, but it would be nonsensical for them to cede monetary control and adopt BTC as legal tender. I'm not sure about mass adoption for commerce, not until we see user-friendly applications that allow for exponential scale. Then we'll see what actual adoption looks like.
If governments will continue with their anti-cash policies, Bitcoin is very likely to become cash 2.0 - a payment method of choice for people who currently have some sort of cash-only business. People will start using Bitcoin as currency more when they'll realize that it's one of the best ways for them. It might not be now, or maybe people just don't think about it too much, but it's very likely to change in the future, although I don't expect it to be too massive.