Nope Apple is fine for at least the next 4 years. After that it is all up to Tim Cook!
I think Apple should start searching for a younger successor to take over Tim's position though, it's never too early to bring a visionary on board.
Based on what? If you think Jobs left that much on the table for the company and nobody has to do and wont do anything else in that time, you are dellusional.
You know there is somebody there who is going to do things their way. If they stick to a 3.5" screen on the iPhone in the next 4 years....that will really set them back a long ways.