Earlier quoted context omitted.
There is always room for improvement in hardware and software. And such high end handsets were never meant to be replaced very often, so the drop in sales is not due to technology saturation, but due to more competition becoming better than Apple.
And such high end handsets were never meant to be replaced very often You're joking, right? If that were the case then why the rapid release cycle. Why do all these phones' screen break so easy. Why are all the batteries so terrible. No, I disagree. Here in Australia, I know at least one carrier (Telstra) who will allow you to pay an additional amount (AU$149) 12 months in to a 24 month contract to allow you to upgra…
Competition. The fact that you don't need to upgrade doesn't mean you shouldn't be able to if you want to get something newer. Stronger competition forces them to move with good pace. Same as in for example regular PC hardware. Compare it to markets where competition is bad, like gaming consoles. There hardware release cycles are abysmally long.