With as much stock as Elon owns, and accounting for other shares being held by his family members and close friends, I think it is practically impossible for a hostile takeover. A lot of people he trusts would have to stab him in the back.
Even if that were to happen, I think that Tesla would be extremely expensive to take-out. The board members have their eyes set on a hundred billion dollar market cap (or more). Going to be hard to convince them to quit now for 5 or 6. Some for sure would be interested, but not enough to overthrow Elon.