Of course, voice acting can make or break a game--when done well, it adds a whole new layer of life to the characters. When done poorly, it makes it difficult for the player to sit through the game. Pokémon could potentially benefit from some voice acting, at least in major scenes.
That being said, they won't even include all the Pokémon in SwSh's data, so there's no way these games will include voice acting. Voice acting is expensive to get, and requires a lot of quality control.