But bitcoin is not the only currency in El Salvador, they are still using USD along with bitcoin and we don't know which currency is most commonly used there. Bitcoin or USD? But as we can see, the president of El Salvador is using bitcoin as an investment rather than a currency. According to a recent report, their investment has brought a profit of up to 50% and they still buy bitcoin every day with investment goals.
Outside of El Salvador, I don't think any developed country will accept bitcoin as legal tender, it's almost unlikely.
Indeed El Savador government more priority bitcoin as investment assets but they had adopt bitcoin for legal payment currency transaction and all sectors accepted bitcoin. Bitcoin become the main investment by El Savador and giving space become legal currency transaction will make easily for their citizen accepted bitcoin for main country investment assets for the future with increasing profitable more than 50% since keep accumulate when bitcoin dropping under $20k.
I think USD dominance difficult stopping by some countries has ideas to make bitcoin as legal currency transaction, so far only El Savador and small African country adopted bitcoin as legal currency transaction and biggest country in European or Asian still not acceptable yet bitcoin will be their legal currency transaction in the future.