Bitcoin will exist as long as there's one or at least few computers running a bitcoin full node. What could possibly stop this? Probably a global blackout or a huge EMP(electromagnetic pulse)[1] or something.
[1] https://en.wikipedia.org/wiki/Electromagnetic_pulse
[1] https://en.wikipedia.org/wiki/Electromagnetic_pulse
yes that is pretty much it but it would have to be significantly bigger than the one in oceans 11
Seriously though, the only thing is a worldwide internet collapse and blackout,
other than that there will always be people willing to mine Bitcoin,
look at dogecoin, people are still "using" it.