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You miss the entire point of 4K and it has nothing to do with the resolution. It has to do with the wider color gamut and HDR. That makes a much bigger difference than 2K vs. 4K resolution.

You really need to educate yourself a bit on video tech, especially if you are selling it to customers. The marketing right now is very confusing to customers (and apparently to dealers as well).
There are a lot of lies pop'n up now on TV boxes about what features it has and what it can do. You have to really look close and pay attention. TVs saying they are HDR when they actually are not - I've seen TVs with regular panels sporting this and just because they can 'process' and HDR signal, they say they are HDR capable. And recently have seen a 32" LG TV that said HDR, because they renamed the 'contrast enhancer' feature as HDR. Very dirty marketing BS.

As far as 8K goes, yeah it is stupid. AFAIK it is just a resolution increase and nothing more. And that just isn't going to matter at all for most viewing distances and TV sizes in a home vs. 4K. You will need a situation where the display is filling you entire field of view - like a large format monitor (30"+) sitting at a desk 1-2 meters away. Or a dedicated theater room with a 120"+ display at regular seating distances.
And good luck with being able to deliver 8K content to a consumer. The only way this will be possible is with downloads to a drive to play back. Or streaming 'if' they have a high enough speed 'and' no bottle necks from them to the server host. That last one is important because even if they have a gigabit internet service, doesn't mean there isn't a bottle neck somewhere else that would cause the stream to compress or buffer constantly.

We are just now getting real 4k content in a larger selection. But a lot of people still can not get regular access to it, since it is mostly streaming and you need much faster than a 10Mbps DSL connection to get it correctly. The only real way for many to view true 4K content in all its glory (and not compressed to shit and missing features) is with a UHD bluray player and buying UHD discs (since you can't rent them yet).
It will be many years before 8K could even be doable for most that wanted to try. The infrastructure has to improve in most places here in the US (because our internet sucks) or a new service which allows downloads to a storage drive would have to exist (which I doubt Hollywood will allow because they suck).