1. Korra Learning Bending From Its Source
At the end of the first season of Korra, Avatar Aang appears to Korra and helps her regain her bending. However, since we only see her bending in the Avatar state, it is possible that she hasnt yet broken through whatever block Amon imposed on her. There has been much speculation about whether Korra has truly regained her bending abilities or not. If she still cant water/fire/earthbend, it would be awesome to see her go find the sources of bending to relearn each form. The dragons can teach her firebending, the badger moles can teach her earthbending, and the water spirits can teach her waterbending. Even if she can still bend, going back to the roots of bending would still be a cool way to get her out into the world.