I’d actually like to understand what your definition of stability is.

Depreciating slowly enough to be held until spent or converted to a store of value. That's pretty much the Fed's definition, and it is mine because it's how cash should behave in a barter economy. Use it or lose it. ("Using includes capital investments and lending to spenders, so I'm not denigrating saving and investment.)

Why ignore the USD, or the Euro or GBP or other stable currencies? They are proof that where the politics are stable, credit-based fiat is the currency of choice. What they use elsewhere demonstrates how politically backward those places are.

The more stable a polity, the more like a stable currency the medium of exchange can be. The lira will stop being a medium of exchange when people stop using it as a unit of account and accepting it in payment for goods. What goes on in the markets of Turkey I can't say. We all remember the Russian stores that only accepted "hard" currencies.

Will we evolve from fiat? I don't think so, because fiat is not a way station. Fiat - credit-based money that can be supplied in a quantity that matches the outputs it can finance - is the solution toward which we have been working since the first notched stick was used to record a debt. If and when we don't barter and don't borrow, we won't need money. Then, fiat will be obsolete. Money may be replaced as a way to prove one's entitlement to outputs, but fiat will never be replaced as money, pre-apocalypse anyway.

The thing that is used as money can be a store of value, too. But that's a technological problem. If fiat is impossible for technical reasons, then money must be tied to a store of value rather than the outputs being financed, and that store of value, being the unit of account, can be used as specie. When gold was HODLed, paper promises to deliver gold traded as money. But the credibility of the issuer or the genuineness of the paper were always in doubt, so sometimes specie was preferable as a medium of exchange. That's why I say that fiat requires technological advance. People trust your VISA card more than they trusted the alleged note of a bank in another city.

Trust is enormously valuable, and the technology of trustworthiness is the key to fiat. That's why BTC is so attractive to places where trust is not really practical.

These crappy national currencies you mention have not lost their legal status because political forces sustain them and nothing better is available. I have no doubt that BTC is a better medium of exchange than some of these national currencies. But it is not a good medium of exchange. Lowering the bar does not prove anything about the thing that jumps over it.

It's hard to argue with "perhaps." Perhaps some days pigs will fly. We shall see.