Musk is offering to buy out all stockholders, so if the sale goes through, he will be the sole owner of Twitter, and all current stock holders will receive cash.

On the other hand, the board can easily say "we don't beleive this deal offered by a person who isn't allowed to be a public officer of a company anymore will ever go through, either because he will retract it or because he will be unable to secure funding; and we beleive attempting the deal will hurt stock prices and profits for current shareholders" and then I agree, it would probably be a slam dunk in court.