Source: https://sixcolors.com/post/2020/01/fun-with-charts-a-decade-...
If I've got a product whose sales were falling 5 out of the past 6 years, and whose current sales are 30%+ down from a peak of 6 years ago, I'm pretty worried about it.
I expect the iPad, lacking any new revolutionary functionality, to reach a steady state of (new customer + replacement rate) sales that is some percentage of its peak, pre-saturation sales. If replacement rate is every 4-5 years, this may be below 30% of peak.
This won't mean it isn't successful, just recognizing that existing users don't need to upgrade every year.
/rant over
Only reason I would upgrade is if I break it (unlikely as I don't take it outside very often) or when iOS upgrades stop (which is what happened to two previous iPads I have in a drawer somewhere).
He's right, if the OS itself was more advanced, than even if the same people who own iPads now wouldn't be interested in using those features other than their regular media consumption, it would still open up a new market for the iPad (new target audience). But with its current limitations, it can't do that.