Nothing has been confirmed yet but I feel from what we heard Kageyama could be behind at least part of the Pokémon Legends ZA soundtrack. That would make perfect sense with him having been X&Y's sound director and lead composer.
At least, I feel confident to say what we heard doesn't sound like Ichinose, Adachi or Sato.
Maybe the biggest news we got from ZA's reveal music wise is there seem to be quite a lot of live recording (finally!!!!).
"Lumiose City"'s arrangement seem to feature live brass, piano and winds, I'm not sure about the strings though.
"Berry Picker"'s arrangement is hard to hear so not sure about that one.
The very calm "Battle! (Wild Pokémon)" arrangement also seem to feature live piano and woodwinds, but also live strings I think.
The "Battle! (Trainer)" arrangement very obviously features live electric guitar.
The last theme heard doesn't sound live though.