Saw an article today where they announced the movie, and I was just scrolling through the article going "please let it be a Pete Docter movie so we can get another Michael Giacchino score... please let it be Pete Docter... YES! Pete Docter!!!"
So I think it's a safe bet Michael Giacchino will compose the score.
The protagonist of Soul is Joe Gardner (voiced by Jamie Foxx), a middle school band teacher who has been unable to pursue his true dream of becoming a jazz musician. [...] Jon Batiste will be writing original jazz music for the film, while Oscar-winning composers Trent Reznor and Atticus Ross (The Social Network) will be scoring the film