No one really knows and can accurately predict about the existence of cryptocurrencies but the price on the market says something about its demand and supply. The more people that are willing to purchase bitcoin at a high price, the more it will become valuable in the market- thus increasing its price overtime. If people were to know that bitcoin would last, then everyone would deemed to be a millionaire.
If you are skeptical about investing in bitcoin, then you can always diversify your portfolio by considering other investment mechanisms available in the market and consider bitcoin as a long-term investment.