Funny that the article fails to mention Jony Ive as the obvious successor to Cook. Doesn't it look like Apple has its next "creative CEO" all prepped up?
Jobs did make sure Apple has no power to ever get rid of Ive for any reason, ensuring him an unbreakable tenure. However, to me, it's far more obvious that he will never take on the CEO role because I think he's prepping to retire from Apple in the next few years as there's a reason we've been seeing less and less of him over the past few years, with his strong desire to move back to England with his family and so on.
The only two people that's more obvious to me is Williams and Schiller but I don't think Cook is going to be gone for another decade.