It's a shame, the Satoshi wallets are just the biggest failsafe for SHA2 at this time; if this letter were real and the funds moved it would take away the biggest coal mine canary of our time. I like having the security of a few million coins that no one can get at unless they break the entire project.
When Satoshi's funds move, it's time to change the protocol.
It's not necessary that the first one to move them would be their hacker. It could be Satoshi if he felt there was justifiable danger.
I think if ALL early unhashed public keys are broken, then one could assume something like a quantum computer broke them. If only Satoshi's coins (or those thought to belong to him) move, then it's probably a normal move.
If this is an encrypted gift to support a friend through difficult times, it would not be a hack to decipher it and take the money. This message was sent voluntarily.