Really great points there. A lot of streaming services like Netflix compress 4K so much that even a 1080p Bluray will generally look better, so I wouldn't have high hopes for 8K. Besides, you'd need a fibre connection to really be able to stream that in any sort of decent quality and although fibre is getting more widespread in the UK it's not yet common.
There's also the limitations of the human eye to consider. At some point, you simply can't go any higher unless you're using a magnifying glass to watch your TV. We'll probably reach that point in a couple of decades or so. And then you need to focus on quality rather than resolution.