I assume this will be a specter that haunts us forever... Well, we can sort of hope so at least. Because the other options are all scarier.
I am sure you have done the same thought experiments.
Coins from Satoshi address move with no warning: Eek. This will most likely cause a huge price crash. Even if "Satoshi" appears to explain it it will be a little scary.
If none of the coins move in the next 5 to 10 years from now, they are probably never going to move at all.
If there was ever any intent to move them, ideally, he just burns them (and not by sending to a burn address). There are other methods, and if one wanted miners to have an incentive to further secure the network, one can gradually use intentionally large fees over the next hundred thousand blocks, only the miners would get the coins?
It just seems likely that the coins will simply never move and the longer they don't move, the likelier that is to remain. And it keeps everything simple, nothing moves, nothing is really burned, they are just all where they are. Any coins that have not moved in the last ten years, would seem unlikely they will ever move at all, except for those few miners who were not Satoshi, and there will be news when a coin mined in 2009 moves.