I don't think Satoshi will cash in all of those Bitcoins. Even if he cashed in some of them, the price of Bitcoin would probably drop because people would expect all of the coin to go back into circulation.
You never know when and what the real Satoshi will be thinking,if he really wants those coins he have saved at the beginning he will move now or at a later time and no one can stop him from doing that. The price of bitcoin will crash only if he plans on dumping all of his coins which is highly unlikely other than that if the coins moves we might see a minor correction because of fear that he might dump everything.
Its just your thought that bitcoin has been holded by the Satoshi now moved to other hands. Actually, this will not be truth I think because the He is one speculates first bitcoin will be reach to 10000$ for one bitcoin. As of now it doesn't happened. May be, Its happened he come out to the real world and say the truth.
They just hold some percentage of bitcoin and not for a lot of shares. Up to 1000 bitcoin in my mind. But as you can see a lot of the bitcoins have had by some of the bitmillionaires such as roger ver and winklevii.
Satoshi has owned some btc. It will never same as billgates.