Ok, so this is where i think that the media being viewed still plays the dominant role in the quality.
if im watching a 1080p Blue Ray Rip on my 1080p TV, its going to be optimized for the least amount of fuzz, or dithering etc, its supposed to be Crisp as shit.
that same video on a 4k TV is going to be like watching a standard 480p or less on your 1080p.
to get it full screen, you are literally blowing it up to stretch it out to go full screen on your 4k, which means it should not look the same or better, but worse. pixelated etc.
So unless you are looking at photos from your camera on a 4k tv with a resolution equal or above, or playing video games optimized for 4k, from what i have read and heard on forums etc, the content just isnt there.
I dont mind 720p on my 1080p, as its less of a percentage in resolution upscaling, than 1080p - 4k, but you can still see a difference even on my paltry 46' 1080p LCD between the two.
Im not buying something new till i get a condo, and get something nice, the size i want for the spot its going etc. till then i will rock this 4-5 Yr old LCD that has zero pixels missing and still works great for my Movie and Gaming needs.