Although I doubt that BTC will disappear, in the case of it disappearing I would say that some other promising altcoin like ETH would rise up and take BTC's former place.

For BTC to become worthless, it is going to take a very long time. I believe that BTC will continue to increase in price steadily for some time. So I am just thinking about making profit and learning more about the system at the moment. I am not that worried about the future of BTC.