Think of Mjölnir without Thor. Mjölnir was nothing without Thor, nobody could even move it. Now, put Steve Jobs in place of Thor & Apple in place of Mjölnir, & nothing else changes. That is the level of seriousness we are talking about.
Of course, everyone has to leave someday, so did Steve. Louis-François Cartier & later his grandchildren died, Cartier brand dwindled but was later revived. Something like that might happen with Apple, but Apple operates in the tehnology industry, where what is today a revolution is tomorrow a dead age-old product. Technology world especially gadgets change very very frequently & even though I agree that Apple has a lot of talented employees, I don't think anyone can really replace Steve Jobs & his innovative ideas.
Fact : Since Bill gates has retired, except for the Microsoft Skype Takeover, Microsoft has done nothing that attracted the people, it has been stagnant! & even in the Skype deal, Bill Gates advocated the deal! More on that at http://www.bbc.co.uk/news/business-13434352
So, even though Tim Cook might be a great leader & innovator in his right, he has a daunting task to carry on the legacy of Steve Jobs & deliver on the high expectations of investors, stakeholders & fans/consumers of Apple.
Do you think Apple can continue or will it become stagnant?
P.S. : This is my second post on Steve Jobs leaving Apple, the first one is at http://blog.jewelove.in/2011/08/steve-jobs-apple-jewelove.html