You know, you're right. The secret of Apple has never been in innovation; it's been in execution.
That's my opinion of Apple. They rarely ever come up with anything truly Brand New with a capital B and an N. But they do what they do so well that it almost seems like they did when you first see their stuff in action.
The logical conclusion is that, in spite of what people have been saying, Apple doesn't need to innovate to stay on trajectory; what they need to do is continue to have terrific design and execution.
I wouldn't go quite that far. While I'd say iOS is still arguably a smoother package than Android, the gulf in quality between the two is just about nil these days, and is getting closer and closer with every new release Google makes. As far as features and flexibility go, Android is already starting to outpace iOS in a lot of fundamental ways, and Apple does have to at least keep up with them there if they want to stay competitive.