It's worth noting that VESA DSC compression is available for DP interfaces at 2,3,4:1 allowing all of these on the announced standard. It's visually lossless even in a large screen flicker test so I think we're pretty set, except maybe for newer and more extreme daisy chaining and VR.
That is where some of the most challenging images come from... especially with white 4pt type against highly patterned backgrounds. However, frankly with a jeweler's loupe even on the most difficult images, I can't tell the difference flickering between compressed and uncompressed at 4:1. If you think about it, H264 is 100:1 compression (PNG 20:1) so it's not surprising that human eye visibility (especially at 10bit HDR and 8k) is excellent.
For a quantitative estimate, PSNR is ~40dB even on fairly extreme images, which means less that those +/-1 code for 8bit sRGB. I'd expect even better from 10bit and natural images to be >45dB.
Given what you have said, I am willing to be optimistic and no longer associate DSC with4:2:0 TV screens displaying text :)
In particular your mention of PNG reminds me that it is lossless, so the idea of "visually lossless" at a much lower ~4:1 compression ratio seems more reasonable to me now.
