If we dare to face the truth, the idea of bitcoin becoming a legitimate global currency is really a pipe dream. Governments will never accept a currency they cannot control and they have no shortage of better solutions. There is no reason for them to favor a currency they did not create and cannot control.
Additionally, bitcoin has too many limitations to be a currency as it can only process 7-10 transactions per second, which is too slow compared to traditional payment systems like Visa or MasterCard, let alone compared to altcoins.
Given Bitcoin's decentralized nature and security, it is more suitable as a store of value, an asset like gold.
Then why did El Salvador adopt Bitcoin as legal tender? If it did it, any other country can do it. It's just that most governments are skeptical of using Bitcoin as a currency. They prefer people to adopt it as a store of value just to "prevent" BTC from gaining dominance over Fiat. So far, their efforts are working as Fiat is still King. I wouldn't expect things to change anytime soon.
If there's going to be another country that will adopt Bitcoin as legal tender, that would be a developing (third-world) country. Developed countries such as France, UK, Germany, the US, and Japan won't even bother trying to make Bitcoin legal tender. It's just not worth it. After all, they have thriving economies. Let us be grateful that at least we have an escape route from the centralized financial system. Things would've been much worse if Bitcoin didn't exist. Kudos to Satoshi to wherever he/she is.