Even though they may start coming out with 8K TVs I think to have it be of any benefit there will need to be 8K sources. At present 4K UHD Blu-ray is quite amazing and streaming 4K still doesn’t quite live up to it. I think it will be quite some time before you see any 8K source material and as physical media is on the down slide I’m not sure you will ever see 8K Blu-ray. That means it will have to be streamed which will probably require higher bandwidth etc. so IMHO it will be a long while.

Besides that to really see a difference between 4K and 8K that is beneficial you would need to sit much closer to your TV or have a much larger one.
All that said I think you are pretty safe in getting a M UHD722 as it should give you a few good years of service.

My gear: Trinnov CI, 271, 8000.1(SEs), 7200.1 HC (SE), 320s, 3200s, Seaton F18 subs, MS200 (2nd zone), 218, 210.
Other: JVC RS-4100 projector, Lumagen Pro Radiance, Panamorph DCR anamorphic lens, Stewart G4 130 screen, Kaleidescape Strato K, Rvolution 4K player and Zapitti NAS, Oppo BDP-203,Roon Nucleus