I know I'm missing something here and you will all point it out quickly.

If/when I move to 4K for my system...my plan is to either use the native smart TV capabilities or feed an HDMI input on the TV with Apple TV, Roku, etc. The 4K sets I have looked at all have an optical audio output on them. I would simply feed that to my 861v8 as a digital source and have the same / similar 5.1 signal that my HD621 previously peeled off. Would this work and how large of a hit in sound quality am I going to take? This scenario is at least a year away for me...

Theater - 861v8, 621, Oppo BD83, 8K front 7200s back, 7200HC with 5200s on the sides, SW 5500
Family Room - 218, OG 8K Pair
Desktop/office system Media Source 600, 3100s with SW1600
Focal Stellia with Arche Amp and 218 for critical listening
Prime Headphone Amp and Power Supply for desktop headphone listening with Meze Empyrean