Well the way I see it, bitcoin isn't really a currency; Bitcoin is an investment. I mean, think about it! When the idea of what bitcoin was going to be was being formed, it didn't become something that you go out and buy you groceries with, its not stable enough to be that.
Thats an accurate description of the status quo. But Bitcoin's high value would never work if there wasnt' a myth that makes people invest in it, and that myth is actually the vision that at some point in the future, Bitcoin will be "massively used" as a currency.
That's why I don't agree to your conclusion:
That is why bitcoin isn't going to ever replace something like the euro or the US dollar because their price change is slow and predictable, Bitcoin is something you buy in to.
Because for the myth to continue to work, there will be an incentive to work on solutions for a more stable price, like "partial backing" of the Bitcoin value by digital goods. Also, liquidity in the case of mass adoption will be higher and that will limit volatility - we already are seeing much less volatility than in 2013/14.
So countries and central banks shouldn't ignore Bitcoin: they should integrate it to their economy.