7. Korra Grown Up
While one of the biggest strengths of Avatar: The Last Airbender was that the entire series was set over just one year, it would have been nice to see some of the Aang Gang's later years. Similarly, it would be interesting to see Korra older, as a fully-fledged Avatar. We've never really seen the world with a proper Avatar, only one in training. Since the creators have stated that each of the four books of The Legend of Korra will be a standalone story, it is very probable that there will be larger time gaps and that we will actually get to see Korra take her place as Avatar.