For me, there are 2 things that bitcoin would be gone. first is time, as time goes by the risk and the amount of bitcoins could decrease or increase as well, but there would be a time that bitcoin would reach its limit at start to fall down and be forgotten. And second is the other virtual money, as other virtual money increase its value, the people are converting and starting to switch to the other fresh and possible good outcome or value that it could give them.