2. Changes in Regulations or Complete Bitcoin Bans:
Another risk that could wipe out Bitcoin is the imposition of strict regulations or an outright ban in major countries. While Bitcoin is legal in most places today, a country like the U.S., China, or a large international body like the UN could make Bitcoin illegal, severely affecting its value and use. This could create huge problems for the global Bitcoin ecosystem.
Complete bitcoin ban is only an illusion, it is too late for that to happen. China, US or even EU banning bitcoin would affect the markets actually, but it would not be the end of bitcoin, other countries are continually adopting it and it would bounce back like it always does. Even if they ban it, this does not stop holders from these countries to continue holding their bitcoin, nor would it stop them from travelling to countries where it is legal to cash in when they want.
If Bitcoin gets banned, could we expect another cryptocurrency to take its place? Could a government-controlled digital currency replace Bitcoin?
Some shitcoins forked from bitcoin like BCH has failed to meet up to bitcoin and such would happen to any new coin that is forked from the bitcoin source code to replace it, it would be very hard to get any coin as near-perfect as bitcoin if ever bitcoin goes down(which I'm not seeing its possibility).
4. The Emergence of a New, Superior Cryptocurrency:
This would be hard to achieve, although I'm not negating innovation, but it would really be very hard to create something superior to bitcoin which would gain global attention and trust like bitcoin has achieved.