Retina
Although my eyes don’t agree with the premise that Apple’s current retina math is wrong, I do agree that what Apple calls a retina display today will not be the last word in high resolution displays.
If nothing else, the current definition is too dependent on viewing distance. Sure, you usually view a given display from some typical distance, but anyone who sweats every single pixel in a design - and probably lots of people who don’t - has spent time getting up close and personal with a display. A few years from now, once every product Apple sells has what they call a retina display today, I can certainly see Apple introducing the next retina display. One where you can’t see individual pixels no matter how close you get.
But why stop there?
Imagine the day when you can pull out a magnifying glass to check out a picture on your iPad, and instead of seeing pixels, you see a whole world of perfectly resolved detail that you didn’t even know existed.