You're leaving out a key point: Linux is not a company and Linus's "career" does not depend on a company. It depends on enough individual people choosing to work on Linux to keep it technically competitive. I have not seen any sign of Linux suffering technically because people who could make valuable contributions are not doing so.
So even if you are a Linus Torvalds, it may only be a matter of time before you find yourself sidelined. I will be surprised if Linus's career ends on his own terms.