Well I'm not thinking about natural disasters here, I'm talking about..what if one day a glitch is found and BTC will value zero? Is technical possible? I'd say nothing is impossible even if it may seem so right now.
And regarding the private keys, they are impossible to break, but do you think they will still be impossible in 50-100 years? I have my doubts; but of course it's not something we should worry about in our lifetime
i don't think it's possible for the value to suddenly go to zero, just because they found a glitch or exploit or anything, someone will always buy cheap bitcoin, i know i would do it lol, i remember there was a bug in the past for bitcoin, but they fixed it without effect on the value, so you see we have already an example what would happen in your scenario