This is a serious discussion. I mean, after I've seen how bitcoin (and other cryptos as well) got dumped badly after an irrelevant law that makes ICOs illegal. I can only imagine now what would happen If more countries do the same thing and It could get worst by make itself bitcoin illegal. Whether we like to admit it or not, most of people would sell everything they have once its made illegal, some may continue to fight the central banking but the sad reality is that as soon as people start making profits, they will dump it and move on.
Well for me, Yes It is possible and we must be ready for this, no matter what we do if all of the government agencies like SEC and the alliance of governments will ban Bitcoin then we have no choice but to move on. Bitcoin can still be used again but on the under the table trasactions. I don't know how people.
But in my opinion it is unlikely to happen because it is the most trusted desentralized network and the most stand alone banks.