I heard that Satoshi holds over 1M bitcoin on his wallets, he better be alive and active somehow. A theft of 1M btc would cause chaos. Well it wouldn't change how bitcoin works, but you get my point, it is no good. We can neither confiscate the bitcoin or hold it somehow (even if there is a way to do so, it would not bring any good reputation to the situation). We can't transfer the old addy format to the new one obviously. We are left with the option to wait and see whoever gets it first, China, Russia, US..?
Quantum computing! Well let me assure you that this piece of technology is not going to be available for a group of hackers. This technology will be available only to it's developers. What makes you think that the first point of use will be Satoshi's wallet? Especially when everything can be tracked in the Blockchain!
I don't see a reason for Satoshi's wallet to be targeted by the organisation which are legitimate. Unless quantum computing becomes cheaper and available to any random persons, I don't see a threat at all!