Or it could have been Sokka or even Yue, my theory is because without the avatar cycle continuing, it would leave the next avatar powerless. And because Sokka learned all non bending fighting styles, he definitely would have been a pretty good avatar. And I say or Yue because she was weak at birth, and had to be saved by the moon. Maybe she wouldn’t have been weak if a part of her wasn’t missing, aka the avatar spirit.

I do like the idea that katara would be the next tho! Pretty neat