Are you kidding? Apple has only half the market of smart phones (and that market itself is growing quickly), and only single digit market share in PCs. And people actually replace their phones and their PCs over a few years. They can keep this up.
Most personal usage of PC laptops are mostly performing tasks that the iPad can do. And the iPad is getting more versatile faster than regular people are using PCs for more tasks. Apple hasn't maxed out their iPad business until iPads have completely displaced PCs.
Second: iPhone.
While the iPhone's market share of smart phones is about half, that market is growing. The iPhone's market share of all phones is very small. Also, keep in mind that the iPhone is Apple's strongest and most profitable business.
Third: Macs
Apple has only single digit market share here. Loads of room for growth, even at their current astounding, competition obliterating, growth rate. By no sensible metric is Apple close to capping out.
That seems very challenging as Chinese and Indian consumers become a larger fraction of their revenue, and as Android puts constant pressure on their smartphone business.
Someone almost always ends up with those legacy devices, usually someone with a dumber genetation of phones, so at least part of that replacement cycle ends up being growth.
