one is regulatory adoption that all countries or at least most of the countries decide to use cryptos as the only legal tender and they decide to forgo their traditional fiats, this option seems unlikely as no country would want to lose power by themselves
Funny you should mention that, with the news coming out a few hours ago of El Salvador being the first country in the world to propose to recognize bitcoin as legal tender. I agree very few countries, if any, will give up their fiat monetary system, but that's not to say bitcoin cannot also be accepted as legal tender in all these countries, especially given that bitcoin is already being accepted by traders and merchants in these countries.
Not talking about its investment value but if tomorrow there is an apocalypse, chances are only people holding gold would be able to buy anything.
No chance. In an apocalyptic event such as a meteor strike, nuclear war, massive solar flare, etc., then all monetary systems will be worthless. People will barter for food, clean water, shelter, medicines, fuel, and weapons primarily. Fiat, bitcoin, precious metals, etc., will all be equally worthless.
It is unlikely that we will ever wait for the global adoption of cryptocurrency by states and their bodies. Most likely, a decentralized cryptocurrency will be the lot of ordinary people and partly of business structures. Governments will use their central bank stablecoins instead of cryptocurrencies.
El Salvador does not have its own currency. The dollar is used there as money. Therefore, they can use Bitcoin without any problems. However, almost all full-fledged states have their own currency and they will never give up on it. At the same time, cryptocurrency may well walk in society along with the currency of states.