Satoshi Nakamoto if is still alive and has access to his bitcoin, will have no reason to dump all of his coins on the market. He has no reason to sell all because he won't be able to use all of such massive money after cashing out. As a Bitcoin founder, it's reasonable if his main priority is holding his bitcoins.
I think that whomever controlled the private key for the genesis block won't been seen for a very long time, if at all. I'm preety sure the individual/s who started bitcoin, had a vision that far surpassed the length of their own lifespans and satoshi is obviously not that dumb enough to trade his Bitcoin for fiat and that is the whole point of BTC.