It is really cool to predict that we could see more millionaire's when the price of bitcoin reach half a million dollars but it will be really interesting to know how many would be holding on to their coins at that time,it is really difficult to tell that,people who started out with bitcoin knows the same exact thing,having thousands of bitcoin is not a big thing when it started and most of them sold off even before the big rallies started ,so it will happen again,people would sell with every price rise and people who has the guts to hold for a longer time might be millionaires.