One thing I really would like to see, though, are some flashbacks or something to the original characters. As much as I appreciate this show's ability to exist on its own, I couldn't help but miss the original crew.
There is a graphic-novel trilogy in the works called The Promise
which is set a year after "Sozin's Comet" and tells the canonical further adventures of the original cast, as well as laying groundwork for the world of Korra
. Volume 1 is already out, Vol. 2 comes out next month (IIRC), and Vol. 3 is slated for September.