Still of relevance: the "when will 4k matter to you?" chart.

http://s3.carltonbale.com/resolution_chart.html

Short version: you might get some benefit from an 8k tv (and associated 8k media if/when it arrives) if you're routinely sitting closer than 5' from your 80" television. Otherwise, not so much.

I generally try to avoid dissing new technology/software/ideas, but really, 8k TVs appear on the face of it to be pretty pointless. You literally won't be able to tell the difference between a 4k and an 8k film if you're sitting at a reasonable distance from a normal-sized TV.

(I'm defining "normal-sized" as "55 inches or smaller" here. If in actual fact lots of people are buying 90" TVs that changes things.)

For reference, I've been a video professional for 20 years, I have a reasonably large television in a not-massive living room, and in my living room I can just about tell the difference between 720p and 1080p content playing on it, if the source is high-quality and I'm concentrating. The resolution has to drop down to 480p or less before I find it starts actively interfering with my enjoyment of whatever I'm watching.