Funny enough, if you exclude the bitcoins that are lost in forgotten wallets (or the keys are stored in a hard drive sitting in some landfill), 15 million millionaires all trying to buy a single bitcoin would not be able to, there's just not enough in circulation.

John MacAfee (Curse his soul for creating the MacAfee virus that infects every pre-built computer) is a smart guy, and James Altucher's comment really points out the logic of the prediction.