Bloomberg:

Apple rarely discusses succession planning, and when asked about it at the company’s most recent shareholder meeting, Cook said “passing the baton” wisely is one of his most crucial responsibilities. He also said succession planning for all key executive roles has been on the agenda at every Apple board meeting in recent years, though he didn’t identify any potential candidates.

Bloomberg walks through the leadership hierarchy at Apple, offering highlights for each person.

I think succession planning is absolutely critical, especially to ensure that Apple is not derailed or significantly changed if the day ever came where a change in leadership occurred. I found this walkthrough of top personnel fascinating and enlightening.