Would it make sense just drop a bitdepth of 8 bits already? Especially now when AV1 was just realesed. All right, decoder optimizations and hardware support will come anyway.
Yes, 8 bits is faster to encode/decode but banding ruins a major part of quality gains at quite large range of bitrates.
VP9 8-bits vs 10 bits is a day and night difference.
https://sonnati.files.wordpress.com/2016/06/10bit2.png
https://sonnati.wordpress.com/2016/0...ntion-part-ii/
Even VP9/HEVC 10-12bit are already so advanced to produce block-free video even at quite low bitrates.
I wouldn't be surprised if AV1 8 bits would look worse than VP9/HEVC 10-12 bits (or just comparable)