The real test will be to see if you can tell the difference between real "4K" program material and upscaled 1080p program material from your normal viewing distance.
It is also possible that TV manufacturers really don't care about the picture quality of 1080p TVs anymore since that's not the hot market segment right now, so they're putting cheaper LCD panels and cheaper image processing into 1080p sets in order to sell them at a lower price, and putting better quality components into the "4K" sets.
I've heard claims that the last generation of plasma TVs were also purposely cheapened-out in order to make LCD sets look better when viewed side-by-side in stores, in order to shake off the still-commonly-held belief that "plasma TVs look better than LCD TVs".
There is actually a real 4K standard used in movie production: 4096x2160. I guess they had some computer geeks on hand who remembered that 4096 bytes = 4K, so that's where the name came from. But that's a slightly wider aspect ratio than 16:9, so when they cropped it down to 16:9 for consumer TVs it became 3840x2160 -- but they kept calling it "4K" anyway even though it's no longer 4000+ pixels across.
Anyway, a really big problem in the lack of true 4K program material is that ever since movie production switched from 35mm film to digital in the early 2000s, they've been using 2K resolution for the cinema masters. Even many movies being released today are still only produced in 2K. So it will be forever impossible to create true 4K versions of many movies from the 2000s and 2010s -- not like older movies where they can just re-scan the film at a higher resolution.
It's just like all the music in the '80s and '90s that was recorded in 16-bit/48 kHz digital. The big push today in the audiophile world is 24-bit/96 kHz "hi-res" music, but how are you going to get 24/96 out of material that was 16/48 to begin with? You can't, not like older albums where they can go back to the analog master tapes and re-transfer them at a higher sampling rate.
