Having seen 1080p stretch and play nicely on a 30 feet cinema screen, and not being much worse looking from regular Hollywood titles even for front seat viewing, I don't see the allure of 8K even for "future-proofing".
Sure, monitors and tvs might improve their resolution in the future. But I don't se human eyes improving much (regarding angular resolution vs distance) or houses getting any bigger to fit a 30ft tv.
4K is good for reframing (cropping) and higher detail, but after some point enough is enough.