I expect he's kind of buggered there. He likes the X name for more than just twitter so he won't want to lose control of it. At the same time twitter would be hard pressed to justify using a domain they don't control especially after the wework scandal (or a small part of it) about the same thing.
Sure, but twitter is not financialy stable and if it goes bankrupt then it's not Musk who decides what to do with a gifted x.com; it's used in a way that makes twitter the most value for the shareholders not the majority shareholeder. And as i said (with reguard to wework) if it's not gifted and with the knowledge of the abuses that a shareholder who is lending(and by lending i mean any convoluted contract that leaves Musk in control of it) a company a key asset can inflict on a company, then it's easy for minority shareholders to sue or even agencies to step in.