Eventually, when everything is traded and priced in bitcoin, bitcoin becomes an objective unit of value. At that point bitcoin is the only thing that is not volatile, and volatility of everything else is measured against it.
Volatility is an an inherent property of an asset/currency/whatever(stddev of (log)returns), as long as you have a fixed and distinct numeraire.
Sure, you can argue that bitcoin may _be_ the numeraire one day, but what's the path towards that when it's so useless as a currency presently?
Either it's good as a currency, or it's good as a savings vehicle.
You seem to be confused about which line you're pushing
Of course there is, for example it would be necessary for it to be useful as a medium of exchange. Which, bitcoin certainly isn't.
I can't purchase, for example, >50% of the basket of goods that comprise the CPI with bitcoin.
Sure, you can argue that anything which can facilitate more than 0 exchanges with more than 0 counterparties is, at least ephemerally, a currency. But if you're arguing that, you've already lost.