Extremely unlikely there will be any disc format beyond 4K. There is no 6K format. If and when 8K content is available it will be thru steaming or broadcasting.
The limit of technology? The sky is the limit I guess. The limit of the human eye? That would be 8K which was chosen based on research into the human vision system. For home screens there is no need to go beyond that.
Media: LG 88" 8K OLED Z9 / Denon AVR-X8500H 7.1.4 / Oppo UDP-203 / Nvidia SHIELD (2017) / Apple TV 4K / Sony 4K FMP-X10 / Gaming PC (Threadripper 1950X / 2x GeForce GTX 1080 Ti SLI) / PlayStation 4 Pro with PS VR / PlayStation (original)
Family: Sony 85" 4K XBR-85X900F / Denon AVR-X3400H 5.1 / Nvidia SHIELD (2017) / Apple TV 4K / C64 Mini - Game: LG 77" 4K OLED C8 / Denon AVR-X3400H 5.1 / Nvidia SHIELD (2017) / Apple TV 4K