Actually nobody knows if he is really holding more than 500k bitcoins, but there are a lot of conspiracies saying that he does, but it is a little bit weird and there is no way to check it to see if it is real or only a conspiracy.
And no, there is no way to know who has the most amount of bitcoin, so this thread is useless, there is no way to check it and see who is the most millionaire in here, lol.
Just imagine, a lot of people would try to hack that poor guy's wallet..