This is the question that this Forbes article addresses. It talks about how Steve Jobs, obviously, can't remain the CEO of Apple forever. Somebody has to eventually takeover the vast computer company. But who? Back in the 1980s somebody did take Apple from Steve, and that was a disaster. It was Pepsi President John Sculley, who was Jobs' apprentice. Then, in 1985, Sculley kicked Jobs out, took a hold of Apple, and basically flushed it down the toilet. 10 years later, Jobs got control back, and Apple flew back to the top as one of the kings of computing and media players.
Who else could do something so extremely positive for a company? Who else could bring Apple up from the bottom and back to the top so successfully? Well, Forbes isn't sure that Apple will be able to find such a well-rounded and smart leader: "Apple will need much more than a skilled manager. 'The new person will have to fit that culture like a glove, if that person comes in and tries to change the culture, forget it, it's over,' Sweeney says. 'The passion, the creativity ... none of that can change.'"
Even more alarming than the fact that Steve Jobs is most likely not replaceable, is what the "Fake Steve Jobs" mentioned in this piece, about halfway down the page. He said that he'd "be surprised if Jobs was CEO by the end of the year due to health concerns." Sure, Apple says that its just a "common bug", but of course they'd say that, even if it was serious. Steve's appearance was trivial at WWDC, but I don't think that Jobs'll leave just because of that. Only time will tell. Until then, get well soon, Jobsy!