The upgrade cycle back when they were on Intel simply did not make sense. So far, we don't have any indication that they want to move on a yearly upgrade cycle (the last Mac Mini was released nearly two years ago now), but I really hope that's what happens. Nobody forces me to upgrade. But I'm glad better products keep on coming out. And I'm glad the used market will become more interesting.
Take the Mac Pro for example.
This is the best computer in Apple's lineup. It's supposed to shine. It's supposed to tell the competition : we stand on top of the mountain and you don't. Well, well... it does anything but that. Hasn't been updated in 3 years. Hadn't been updated in 6 years before that. Now it's ridiculous, because you can pay 4X less and just buy a Mac Studio instead, and even the best upgrades on the CPU/GPU on the Mac Studio make it a bit overpriced compared to a similarly spec'ed PC. So clearly, the Mac Pro is overpriced as f**k.