A sudden withdrawal of of 1 million (or large gradual withdrawals) should be regarded as an attack on Bitcoin.
How is withdrawing 1 million BTC an "attack" on bitcoin? It's Satoshi's money. Let him do whatever he wants with his money. He can spend it all on blackjack and hookers and hell do I care how he wants to spend it.
Right, let him sleep in peace. Don't disturb him to say 'freeze his/her 1 Millions Bitcoin until he is active', it is Satoshi's money and he will decide when he will withdraw his money from the market. The last 10 years he is holding from an unknown source.