Even on the insanely expensive 70" 4K tvs, it's still only 4k. That leaves print: I'm just curious what print houses will print at these resolutions? Even the highly regarded mpixpro lab made me send them an 8 bit sRGB JPG for my 24x36 print, and much to my surprise, at 24MP, it turned out just fine. Could it have looked better? Sure, but after playing around a LOT with the images (including re-shooting the scene zoomed in and stitching images to get a much higher effective pixel count), I'm convinced that this is due to the JPG requirement, not pixel count.
People are going to buy what they want, and I'm not going to try to stop them. I just don't understand the need to go any higher. If you are consistently cropping for added zoom, you have the wrong lens or are standing in the wrong place.
If you shoot for large format prints, you have the wrong camera, you should be shooting medium format.
I keep hearing people talk about needing high frame rates (makes sense) and high MP (why?) for sports. Even using the lossless compression, those are roughly 50MB files.
50MB x 10FPS = 500MB/s. Good luck finding a card to keep up with that. You'd need a 1-2GB insanely fast buffer in the camera just to be able to shoot for 2 seconds.