what happens if the next 10 years, bitcoin disappeared and worthless?
If Bitcoin would disappear then nothing would really happen. Bitcoin would be gone and people just have to move on with their lives. of course people would be mad because they have invested money into Bitcoin and did not make it back.
there must be a factor in why bitcoin could die the user may not be more than 5 million people will leave the bitcoin for no reason?
of course they do not want to lose. so I think only a few people out of bitcoin. with such a bitcoin will be difficult to disappear. there needs to be a compelling reason.