In my reviews, I’ve started posting images at sizes up to 28 megapixels (for 3:2 aspect ratio images). That is, the new largest size for viewing is now 6480 x 4320.
4K = 3840 X 2160
5K = 5120 X 2880 (iMac 5K)
8K = 7680 X 4320
I’ve chosen 28 megapixels because at 6480 x 4320, the 3:2 aspect ratio image will fill the screen vertically with its 4320 pixels (actually overflow slightly due to the menu bar and such).
So when an iMac 8K appears, images will look just as stunning as on today’s iMac 5K, but there will be a size to fit the screen (2.25X as many pixels as to fit the screen on the iMac 5K).
See What’s the Best Way to Enjoy Images at their Finest?. The future for jaw-dropping viewing pleasure is NOT (and will never be) prints with their dull dynamic range and marginal color gamut; it is 8K television and 8K computer displays. And perhaps 16K a decade from now.