My understanding is that today's HDR sensors and displays can do ~13 stops of dynamic range, while humans can see at least ~20, though I'm not sure how to trans

My understanding is that today's HDR sensors and displays can do ~13 stops of dynamic range, while humans can see at least ~20, though I'm not sure how to translate that into how much additional bit depth ought to be needed (naively, I might guess at 48 bits being enough). I don't see why we'd stop at 60fps when 120 or even 240 Hz displays are already available. Also 8k displays already exist. The codecs also have tunable quality, and obviously no one is sending lossless video. So we can always increase the quality level when encoding. So it's true in 2023 (especially since no one will stream that high of quality to you), but one can easily imagine boring incremental technology improvements that would demand more. There's plenty of room for video quality to increase before we reach the limitations of human eyes.