Here are some possibilities and the arguments for and against them:
Possible Next Benders:
* Metalbender: Metalbending is a rare and powerful sub-bending of Earthbending. With the rise of industrialization in the Avatar world, it could be an important power for future generations. Argument for: It's a powerful and visually interesting bending style. Argument against: Metalbending's popularity might overshadow other types of bending.
* Airbender: Airbending has been limited in the Avatar universe, and it could be interesting to see a resurgence of the Air Nomads and their unique approach to bending. Argument for: A revitalized Air Nation would offer a new perspective on the world. Argument against: It might be too similar to the current Avatar, Korra.
* Waterbender: With the ocean being a vast and unexplored territory, waterbending could offer new possibilities and challenges. Argument for: The oceans hold many secrets and potential dangers. Argument against: Might feel too similar to previous Avatars.
* New Type of Bender: It's entirely possible that a new type of bending could be introduced. This would be a risky but potentially exciting choice. Argument for: A new type of bending could create new and unique challenges and opportunities. Argument against: It could be difficult to integrate a new bending style into the existing lore.
Ultimately, the choice of the next Avatar's bending ability will depend on the direction the creators want to take the story. They will need to consider what kind of challenges and opportunities this new Avatar will face, and how their bending abilities will contribute to the world.
It's an exciting prospect, and it's fun to speculate!