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.