You would have to be foolish to. However much value may be created, Musk has shown he will try to wriggle out of deals he made when he thinks he can get away with not meeting his obligations to his counterparties. Delaware courts wouldn’t let him welch on the merger, and I expect the execs he fired “for cause” will successfully hold him to their agreements in the end. You, as the employee in a closely held private company, will have no such leverage. Musk could promise all the upside in the world, but even if everything works out he’ll just screw you out of your share of it.