I think your statement is not entirely true, because Japan was actually the first country that accepted Bitcoin as a "Currency" and even if some other countries does not accept it as a legal tender, people still buy and sell Bitcoin without their permission. Examples of countries where this is happening is Zimbabwe / Yugoslavia / Venezuela / Hungary ...where they are struggling with hyperinflation.
Most of these people are forced to do this, because they need to protect their wealth against a failing Fiat currency. So yes... other countries will also do this, because more and more countries are struggling economically and hyperinflation is becoming more common now.

That's good to know. The more countries adopt Bitcoin as legal tender, the higher its demand will be. It makes sense for third-world countries to adopt Bitcoin as legal tender since their own currencies are dying because of hyperinflation. For developed countries like the US and the UK, that's another story. It's very unlikely Bitcoin will replace Fiat on developed countries, since governments see no need to make the switch. The US Dollar is still powerful even with Bitcoin in play. What could happen is that developed countries back their currencies to the value of 1 Bitcoin. If they did it with Gold, they can do it with Bitcoin.
Let's see what happens with Bitcoin after the next halving. I'm sure adoption will grow even higher as more countries join the game. Whatever happens, Bitcoin won't be going anywhere thanks to its decentralized and open source nature. Just my opinion
