Still this is a very complex game theory problem even for governments. One government banning Bitcoin might create unprecedented opportunities for other countries. China banning Bitcoin makes sense if you consider their way of governing the people and their whole economic and social system. But will Bitcoin ever be banned by the majority of countries all around the globe? And even if that was the case, cryptocurrency related businesses (mining operations, exchanges etc) will find their place elsewhere. I don't see any chance for cryptocurrencies being banned all around the world. Even think about the administrative effort it would cost a government to really shut down all economic activity involving cryptocurrencies. Besides that, I think we can be pretty certain that there is a good number of countries already that signaled quite obvious there won't be a ban on cryptocurrencies. They might come up with new regulations, but an outright ban can also be very risky in the long run.