I致e been wondering when 4k anime would become a thing; wondering and hoping that some better ones would really shiny in HDR and 4k.

Sounds like it値l be a while to say the least...
Netflix worked with Production IG to do a test 4k+HDR anime and wrote in a fair bit of detail about the issues they hit and changes needed:
https://netflixtechblog.com/bringing...e-fa68105067cd

Pretty good read! (Not checked out Sol Levante yet, but looking forward to seeing it and glad Production IG is behind it).