It depends on what you mean by altcoins. If you mean litecoin, ripple, ethereum, then I think they are too big and well established to disappear. The other smaller coins though pose a much harder question as it relates to their longevity. There may be consolidation in the next 18–24 months that brings the top 20 coins together and filters out the wannabes. So In short, it is my opinion,  that the altcoin market will not crash outright.