This doesn't work in all markets - see Apple servers. Some of their products (desktops, Apple TV) are probably on the wane.
Uber ditched the premium ("Apple") role with Uber-X
Forward looking, I'd be really very surprised to see Apple staying relevant in tech in the next decade as the smartphone revolution fades away and the novelty factor they enjoy or make up as well as market dominance will follow suit.
The MP3 player market and iPods in particular have been swallowed and cannibalized to Apple's discontent by their smartphones and their peers again.
So, it doesn't look rosy for Apple as it's becoming more and more a one trick pony with one single dominant product while the rest are suffering or in steadfast decline and when you take into account that the saturation point for smartphones is approaching, you'll realize that they will need to bring up REALLY something new or face the fate every tech company finds itself sailing the ship through the stagnation storm just to get alive.
There isn't even evidence that the overall trend foe the iPad is lower growth - just that the upgrade cycle is slower.
As for a 'one-trick pony', that statement is certainly false, as Apple has multiple growing product lines.
Also, saturation for smartphones may be approaching in a few markets, but saturation for the iPhone is much much further off, so your prophecy of decline is empty as yet.