Nice Monkey,
I have a UHD 4K disk player and a ton of 4K discs. I'd say easily way over half of the media I watch is 4K, between discs and the bit of streaming I do. That said, I know very few people who have 4K TVs, and definitely don't know anyone who has 4K discs or players. Even I have no desire to move to 8K any time soon. Youtube does have some beautiful 8K videos, but I'm not ditching a great TV just to see some Youtube videos in a bit higher rez. So I have to agree with you, 8K and 4K@120fps features are bonus "nice to haves", but HDMI 2.1 features will be more useful in the near future. I'm not opposed to 8K being available in a device tho, just for future proofing.