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.
I do think he did it already. I have not read the SEC file if there is a timeline on when the asset could be moved but if there is a statement that says it can be moved anytime he likes then he might be selling it gradually that's why we are experiencing price dumps with unknown reasons.
It's all just business for him and it will stay that way. I doubt he is the holder type like many forum members here who will keep it long term and wait for the mainstream to accept BTC as a widespread currency. IIRC, he bought at $36k so if it goes $40k again it might just be dumped to take profits.