If Musk dies tomorrow, I don't see anyone else leading up charge for all the progress in space exploration. No one is gutsy enough to go after Mars landing as much as Musk. I would fear that Mars mission will die out if Musk goes away and we won't see it happening in our life time. All the EV race is also purely due to Tesla lead. No car manufacturer wanted this change and they are all now getting dragged into it. If Musk dies and Tesla goes stagnant, I can bet car manufactured will return to same-old same-old in no time.

I am less worried about Musk "overworking" and more worried about him getting identified as sacrificial scapegot in one of the political fights and get "cancelled".