Its depend on what background of the BTC ceases itself. I dont think its ceases because cryptocurrency is expired or something like that, i believe its ceases because theres an ultimate altcoin that take BTC throne and being adopted as one of world payment system.
Is it really happening now? because if there is a major Altcoin that is able to take over the throne of BTC to be adopted as one of the world's payment systems, this will obviously be very extraordinary, but can it happen and that Altcoin can live well if BTC experiences a big crash?