So you are saying that Bitcoin can't disappear because it will forever be a speculative vehicle with cyclic market? I think both parts are incorrect. First, Bitcoin could stop being so volatile and cyclic and turn into a "boring" asset like gold eventually when people will stop panicking and fomoing as it will lose its novelty factor. Second, being a speculative vehicle alone is not enough for it to survive forever. People could tire of it and find other markets that will be more fresh and exciting.

Humanity is very bad at predicting the future, 100 years ago people imagined today as the world of space colonization, flying cars and robots, but instead we have smartphones and internet. You can't be sure that Bitcoin will survive even 50 years, too many things can change.