Is to go ahead and shop the HDTV and look for UHD with the new HDR feature then use what you have now. For example many have the BluRay with 1080p so just us that and let the UHD upscale it for you. Then in a year, go looking again.
Besides that chart you may have seen shows you may have to sit at 7 or less feet to the screen to see it.
Looking for a new 65" flat screen Smart HDTV but not sure that I want 4k SUHD now because 4K content isn't quite there yet. I've heard that Netflix has 4K content at added cost. I primarily will be watching movies via streaming and dvd. Regular tv viewing will be seen on my downstairs tv. I'm not a gamer so that's not an issue I also believe that I'll need to buy a 4k dvd player.