for the short term there will be a big dump. but no long term impact. I don't think they're all stupid, they will sell gradually and announce all of it after they finish selling it. so no one realizes that they have sold their bitcoins. and when the announcement is published there will be a momentary dump.
short term effect will be very dangerous, it will make market sentiment and faith to bitcoin or crypto market decrease.but for long term i am believe it will become more decentralized and no giant investors or whales controll this market.current price was not elon musk target profits, he will set higher price to double their investment just like tesla long term investment.