Yes you really will not make other bitcoin holders go bankrupt if he sells it, after all I think 1 million BTC is the right of him who can be considered a reward for his very great discovery, but for trade events will definitely panic, but I believe enough that he Will not sell it at once and will not enjoy it for his own life, charity and Bitcoin development will be much more noticed, and even then if he is still alive and will appear, yes I believe that he does not have access to control bitcoin even though he returns.
There is no guarantee that if he were alive he would not sell those bitcoins but does it matter? It's his bitcoin and he can do whatever he wants with it. I find it confusing that people own bitcoin and sell it when the price goes up but they are afraid of Satoshi or whales selling bitcoin. I think that is a bit selfish, IMO.
Agreed that if a large amount of bitcoins were sold into the market, the price would drop sharply but that's how the financial markets work. Is there any market that doesn't get dumped and panicked when whales dump large amounts of assets? If we truly believe in bitcoin, we know that it will absorb any selling pressure and recover over time, there is nothing too serious about whales selling their bitcoins even if it is satoshi's bitcoins.
Satoshi created bitcoin but he cannot modify bitcoin because he gave control of bitcoin to the community, so his presence will not change anything.