I think we're approaching a point in the lifespan of Tesla where is can stand on its own merit and no longer requires Musk to continue making a ridiculous amount of money. However, Musk is integral to the continued innovation and success, the same as Steve Jobs was to Apple. Under Tim Cook, Apple continued to thrive, albeit in a different way.

Regardless, no way will Musk run Twitter on a day-to-day basis, he'll remove the board, replace the CEO with someone he trusts, likely get Jack involved again, and a lot of developers will leave, leaving the company in a better position financially. Musk will likely just guide functionality and policy decisions from afar.