As a rough order of magnitude estimate, if Bitcoin gets to be as big a thing as gold, then it will be worth about $10 trillion. Since there will be about 20 million BTC by then, those individuals will be worth about $50 billion. This is a lot of money to be sure, but there won't be many of those people, and this is not out of line with the world's very highest net worth individuals.
The people who got in after that peak will probably be worth at least an order of magnitude less. And if Bitcoin turns out to be a smaller deal than gold, it might "only" create fortunes worth 9 figures of USD.