I just watched the 2 episodes of legend of Korra, and have been a huge airbender fan for the longest time.
The universe just screams "MAKE ME AN MMORPG DAMMIT". 4 elements = 4 classes, you could probably sub spec for more. Earth -> Metal Bender, or Water -> Blood bending. The new arena game they have (pro bending) just sounds like a competitive arena ladder waiting to happen.
She even has a Polar beardog Epic Mount. Sky Bison Flying mounts.
Raids can fight old enemies like Firelord Ozai and Princess Azula.
Just saying