What else can the co-founder say. Obviously he is not going to say that the price is going to stagnate. I'm not saying that it will not triple, it could, but there is a lot of competition coming from other newer coins and even systems improving the blockchain technology like raiblocks.
Also remember that not always the best technology wins, remember Beta vs. VHS and even Windows. This means that ETH could win other newer and better technologies but also BTC can win them all even when in theory is not the best technology (but is proven).
He could have declined to comment on price, however that would be weird considering he agreed to appear on 'Fast Money' :)