We upgraded our older 1080p high-def box TV to 4k 55" flat screen a couple years back (LG OLED). There is no comparison. The resolution is like looking through a window. Plus, they upscale everything, even old shows of the time broadcast in 480 resolution (4:3 aspect ratio).
As for 8k, I see no need for it unless projecting on a large screen or a huge display in your own dedicated large theater. 4k is great for the 55" to 70" display depending on your seating distance.
I've been promoting 4k for some time on this forum. The prices are dropping dramatically for those who thought they couldn't afford them. Why bother with the inconvenience, noise, hassle, crazy snack prices at theaters when you can have a better experience at home. With a decent inexpensive receiver and surround speakers, you have your own movie experience.
Agree on all points. The store had a couple of 8k models on display just to demonstrate the technology, but the sales guys were quick to emphasize that there is basically no 8k content on the market at this time. What we saw in the store was amazing but it was all specially made demo videos — again, just to demonstrate the technology. I asked how soon 8k might start to appear. Well, no one wants to bet against the rate of advance in such fields, but the sense of the people we talked to was that a bit of content would start to appear within five years but that it will be much longer before 8k content is common. 4k looks like the standard for the foreseeable future.
8k OLEDs are also ridiculously expensive now, but everyone expects prices to decline dramatically as production begins to scale up.