As bandwidth has increased, we've always found ways of utilising it.
4K streams are still heavily compressed compared to their Blu-ray counterparts, but as 4K content grows a lot more people will consume it. 8K is next and even 16k will be not far behind - we'll start seeing that in the next 10 years or less. A 16k stream will
consume well over 1gbit of bandwidth itself.
Of course, I'm not suggesting that 16k will be why we need 8gbit connections but it's just one example of a growing need for more bandwidth. Beyond sheer resolution, audio quality and video quality (likes of HDR) require yet more bandwidth. Technology marches on.