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.
Announcing it can be a weapon for the fall. Anything can also happen, this is what would probably happen, they will sell as later annkice it. But I only see a reason why Elon Musk would want to do this, to either make the market to dump and to support Doge. Just like I predicted Tesla dumped bitcoin for doge, also it can happen like that in a way to continuing supporting doge to rise in price.