If everyone stops using it or if in some way becomes wothless, these are the two situations I think of that could make bitcoin die. But I don't know what could cause something like this, people get used to bitcoin and all benefits that it gives and demand is geting biger all the time.
in addition to that answer bitcoin will die if any country in the ban it. Also if people find another type of bitcoin that is better than it. There is a possibility that people will stop using it if it happen. I think if bitcoin will have more problem and bad issue this could also be the reason for it to die. especially if they didn't fix it as soon.