Vitalik is just saying he has not had "100%" certainty in Crypto which is natural because it's an experimental technology. It is maturing very well with time though and everything seems to be on track. Vitalik is trying to get rid of the weak hands before Metropolis lol jk jk. Easy to hold ETH, if ETH collapses nearly all Crypto will, hold on to the big dog. Crypto is not crashing anytime soon though the Wall Street dudes are just starting to get interested. 
Nobody is 100% sure about crypto, yet the way Vitalik express his opinions is not consistent with the philosophy of blockchain technologies. Dude, we're talking about the creator of the second best coin, ethereum.