Permit me to disagree. I have not so hot vision (contacts, -4.50), and, unlike many people I know, I can clearly distinguish between, say, 720p and 1080p. I just moments ago installed my new 55" 4k Vizio (P series ftw!), and the difference is remarkable. It's fairly noticeable on upscaled 1080p content, but plug in a computer and push some real 4k (read: games), and the difference is remarkable. At a viewing distance of about 10 feet, the difference in clarity is readily apparent. And I'm not alone in this regard. The friends who helped me install this beast are fellow videophiles, and we were all blown away by the difference. I'm about to hop on to netflix to start up my subscription again (haven't had an active netfilx account in years) just so I can stream their 4k content (already have amazon prime), and I'm eagerly awaiting 4k blu ray (not that I'll spend much time swapping discs, as with current blu ray, they'll go in the drive just once, to be ripped, and then get carefully filed away).
Also, I heard many of your arguments years ago when HD was first rearing its head in the market. "There's no content, no one will buy it", "no one will buy it due to lack of content, so no one will make content", "current resolutions are completely sufficient, and no one will see a difference anyway". All wrong. Give it a year or two. Even if 4k blu ray doesn't take off particularly well, expect to see more and more streaming/downloadable 4k content. And, a quick perusal of 4k video on torrent sites show that 4k is already being pushed by the same people who have pushed every other major advance in home video for the last few decades: the porn industry. I couldn't find any 4k movies to download, but if you want to watch people screw in 4k, the future is now.
I'll go ahead and get off your lawn now.