Great point! I own a 4K PS4 and owned the 4K AV8801 (gave it away). Both were sold as 4K at the time, but by the time 4K took hold and gain some popularity, the format (or whatever you call..) has changed so the 4K feature I bought became obsolete with limited usage only!!
Having learnt that lesson, this time around on the 8K thing I thought fool me once shame on them, and I chose the 4K Anthem AVM70, that saved me $500.
I don't need 8K to play game, but even if I did, I would not get into 8K until the dust get settled. I bet most who own the 8K AVRs/AVPs won't be taking advantage of the feature they already paid for, and by the time the contents become popular, their 8K HDMI card may fact the same thing I faced with my first generation 4K *&$%#@!