Well, he has probably been careful to ensure that he can't lose according to his rules. If the USD to bitcoin exchange rate doubled every week for the rest of his life, he can easily maintain the claim that it will still eventually crash. If the exchange rate does crash, then he can say he was right. I can make the same claim about the US dollar. Without a time frame and price in the hypothesis, saying "it is doomed to crash" or "it is doomed to failure" is not a falsifiable statement.