> Governments choose and maintain currencies with low, stable inflation because it's good for the economy and the people at large.
Yes.
> Individuals choose currencies with stable supplies to maintain the value of their wealth.
Individuals are far wiser to invest the majority of their wealth instead of keeping it bundled up in any commodity that has no inherent value. This includes bitcoins, dollars, yen, tulips, pog caps, and gold. Arguably gold has more inherent value than anything else on that list, but again tying capital up in nonproductive activities (commodities) is not only a poor investment, it makes no larger economic sense.
> In nations where cryptocurrencies aren't outlawed, they will prosper, and those governments will have to figure out how to manage an economy with a popular deflationary currency.
This is an argument advanced without any support. Not all cryptocurrencies are deflationary. And no proof is offered that deflationary currency has any advantages whatsoever. Only hand-wavy "citizens prefer stable supply" is advanced, and I'd argue that the majority of citizens that know what they're doing prefer to invest in productive activities anyway.