4. The Rest of the World
When Aang was preparing for his battle with Fire Lord Ozai, he and his friends traveled all over the world, and what a world it was. Some of the best episodes of the first series were the ones where the Aang gang visited a strange new place. With Korra, we haven't really seen anything aside from Republic City. We glimpsed the South Pole briefly, but that's about it. What's going on in the rest of the world? Are the different nations becoming more integrated? Has the industrial revolution spread beyond Republic City's walls? Will we ever meet the descendents of characters like Haru or Teo?