I would think 8k more apropos to medical applications... monitors and such, where one needs access to the finest detail in imaging. Overkill for anything else... at least for the time being.8k exists, but there seems to be no rational reason for it to do so.
I’m unable to rationalize a commercial purpose.
I think anything beyond 720p is a case of diminishing returns. I'd rather have a flawless 720p picture, particularly from cable, than an over-compressed image of any number with "k" next to it....I'm very much inclined to believe that going beyond 4k will be a case of diminishing returns.