It's interesting to see how this is playing out. Libertarians have long argued that government-issued fiat currency is a tool of state oppression. Now we have a real-world experiment demonstrating on a grand scale what happens when you create a currency by consensual fiat. I'd be interested to hear what libertarians think about this: Is Bitcoin truly the kind of currency libertarians have been advocating? Have I misc…
However, I think it's a bit early in the life of cryptocurrencies to make any evaluation about how the experiment is going. To understand why libertarians obsess over currency, I recommend one look at some history[1] instead, and see that fiat currencies have long been associated with war, oppression, and corruption.
To answer your last question, I don't think cryptocurrencies will actually be used unless there is a need for them. If inflation in the U.S. becomes extreme, for example, people will naturally flood to cryptocurrencies as a better store of value and/or way of transporting value. There have already been examples of that happening in countries with currency problems, such as in 2015 when many Argentinians began experimenting with Bitcoin[2].
But for the foreseeable future, most people will probably not notice any big problems using their local currency, and so they will continue to do so.
I personally don't think Bitcoin will last. Instead, another cryptocurrency will take over. Probably many will take turns over the years.
[1] https://en.wikipedia.org/wiki/A_History_of_Money_and_Banking...
[2] https://www.nytimes.com/2015/05/03/magazine/how-bitcoin-is-d...