Man, I'm sure the richest of the rich in this world became rich because of business and multiple investments from different platforms, maybe some invested in bitcoin too. And I think someone can be rich here, but I'm also sure he will try to create business in fiat too just to be among one of the richest. Capitalism makes them rich too btw, in bitcoin or in fiat, it will be the same.
Its undoubtedly that having a single token of bitcoin was a real high worth if it would exchange in fiat. But knowing the richest man alive on earth could possibly be by just dealing full time in bitcoin i bet would take for some time though it isn't impossible but the legalization of bitcoin would be a big factor for it. As far as i know becoming a richest man shouldn't have to focus in a one kind of platform of investment and that's how the richest man alive today does.