While the game will have a free Japanese voice pack at launch for those who prefer the Japanese audio, only the English option was experienced first hand. (cogconnected.com)
I do know that there will be an additional voice pack featuring the cast of Critical Role, which should be an awesome addition. (thatvideogameblog.com)
Also, it's still just a dream of mine right now, but I'd love to put out a Japanese language voice pack. (accessgames-blog.com)