The Legend of Korra
Some possible sets Lego could release:
Pro-bending arena: Includes Mako, Korra, Bolin, Tahno, all in Pro-bending uniform, and Pabu
Air Temple Island: Includes Tenzin, Korra, Pema, Meelo, Ikki, Jinora, Rohan, and Naga
Sato Mobile Chase: Includes Asami, Korra, Mako, Bolin, Pabu, and 2 equalists
Hiroshi's Mecca Tanks: Includes Hiroshi, Asami, Tenzin, Chief Saikhan, and 2 equalists
Equalist Air Ship: Includes Lin, Amon, the Lieutenant, and 2 equalists
Equalist Planes: Includes Genral Iroh and 2 equalists
Korra's Escape: Includes Korra, Naga, and Katara
Republic City Hall: Councilman Tarrlok, Tenzin, and Korra
Here we see weapons used in The Legend of Korra, including Lin's metal ropes or bolas, the Lieutenant's Kali sticks, water-bending, fire-bending, and Asami's electroshock glove.
Other characters in Legend of Korra including Chief Saikhan, Jinora, Ikki, Meelo, General Iroh, Amon/Noatuck, Lin Bei-Fong, The Lieutenant, Hiroshi Sato, Tahno, and Councilman Tarrlok.
Here we see some old faces and new ones appearing in Book 2: Spirits. We can see characters such as Pema, Rohan, Bumi, Kya (Katara and Aang's 3rd child), Katara, Verick (Bolin's "Howard Hughe's" type friend), Tonraq and Senna, Unalaq (Tonraq's brother and Korra's uncle and spiritual trainer), and Unalaq's son Desna and his twin sister Eska.