In my honest opinion I do not think this is possible. Because many people are investing in bitcoin so as bitcoin value depends in supply and demand so if the banksters and governments hold 90% of the supply the value will increase making a lot of people very rich.
what if i told you that there is a high chance that an exchange you use or a merchant gateway or a hardware wallet or even a software wallet can be tied back to a single company with some ownership stake in your coin holding/using solution.. see post above for hints(link provided in previous post)
But is it possible for that to happen? I don't know how much of the people were using the exchange to store their coins but if most of the people were using the wallets means thay can't take our coins without the private keys right?