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.
Yeah a lot of people will be mad because of lost profit but some people will be happy because their altcoin will have a better chance of being used by people who have used bitcoin.