None of the successful founders quit being CEO until their company was firmly #1 in the industry and very profitable - Gates, Ellison et al.
I expect Musk to move to a non-CEO position when Tesla is #1 in the auto industry (2035 ?).
Current top car makers are at about 10M cars annually, so if we say that Tesla sells 0.5M cars this year, they need to grow a factor 20 (this pessimistically assumes no reduction in sales among the current top car makers).
To do so by 2035 (i.e. in 16 years) requires an annual growth of just over 20%.
If Tesla's current annual growth of 50% were to be maintained it would take just 8 years, i.e. 2028...
Gotta ramp up those gigafactory projects...