I believe the genesis block coins are non expendable. It could happen with coins from the next block, of course. Some week hands would get nervous and sell, which could drive the price down temporarily. Nothing major, though, I'd say.

please read and learn:

Lol a few people would panic and frame it as bad news, that he/they are going to rug us all, but the fact remains its only a 21 million cap and millions of Bitcoin has already been lost already so its always going to be less than that available, sure the float could expand temporarily and suppress the market has supply exceeds demand but the price would lower to a point where we are gobbling up his sats and the coins just redispurse and on we go :)

Also one miner should make a pretty penny for securing the block where Satoshi moves his coins other than that not too bothered

The market already assumes the bitcoins altogether totals 21,000,000. So such an event would make a tiny splash and whoever he is would very soon have a lot of dollars and not a lot of bitcoins. This is so unlikely to happen that I'm comfortable dismissing it as impossible.