It's important to note that he does have a few new Pokémon join his team in this series, but they are all obtained through other means:
* Gengar: This Pokémon was previously owned by his friend Goh, who gifted it to Ash.
* Dracovish: Ash was given Dracovish by Leon after it helped him during a battle.
* Lucario: This Pokémon chose Ash as its trainer after being impressed by his battling skills.
It seems like Ash's focus in this series is more on strengthening his existing team and developing his bond with them, rather than acquiring new Pokémon.