2. Aang/Tenzin's Family
It was revealed in The Legend of Korra that Aang and Katara had three children, of which Tenzin was the only Airbender. We glimpsed Bumi, Tenzins older brother, but havent yet seen his sister Kya, rumored to be a waterbender. Fortunately, the show creators have confirmed that they will both show up in Book 2: Spirits. But what about Sokka and (we can only assume) Sukis children? Or Bumi and Kyas kids? It would be great to see the Airbender kids face off against their waterbending cousins.