Yes, in a finite universe it is basically inevitable Apple will run into trouble. But it is a mistake to see in Apple's enormous recent success, or even in Steve Jobs' death, a set-up for its eventual total failure.
While it's right to remember Jobs' life and legacy, what matters is understanding what this giant brought to the modern world. His true success was in transforming pure capitalism into a force that touched people's lives and changed them for what they perceived to be the better.