Regarding 8K TVs, a friend of mine scored a 65" Samsung one on a Black Friday event last year for $1400 (USD). You can find them in that size all over for $1600 and a 55" for $1400. That said, I could tell no difference from my LG 4K OLED as far as pixel video tests. It didn't pop to me like going from 1080p to 4K, or even on PC gaming from a 1080p monitor to a 1440p monitor.
I'm a firm believer that the human eye has a diminished returns capability of seeing ever more increased pixel density resolutions and we've hit it at 8K.
This. I still have a 1080p 65" TV that I'm going to keep until it dies. I sit just about at the limit of where I can distinguish individual pixels, so it seems like going to 4k, before then, would be a waste.
My PC at work has 4k @ 32" and it's borderline too small for the font sizes I liked at 2.5k @ 27". To get the same DPI, I'd need a 4k monitor @ 40". For a work monitor 40" is almost too big. Maybe 35-36" would be a decent compromise.
Anyway, the reason I'm posting here is that the killer app for these high-res panels is lightfield tech, IMO. Not that there's a huge market for lightfield displays, but it's something you need a ton of native resolution, to do well.
That's because once you add a microlens array, it cuts the resolution by about 1/5th to 1/9th in each direction. So, your 16k 2D display suddenly becomes a 2k or 3k lightfield display.