I have heard they have even ordered episodes for a THIRD season of Legend of Korra. Not unrealistic, they do these things pretty far in advance.
I also think the name Amon is derived heavily from Anon, the wannabe hackers/whatever they are. They both wear masks, and only have 1 different letter. A bit surprised I haven't heard it from anyone else yet....
I have read 1 of the 3 The Promise comics, really worth looking at those. The fight scenes are hard to show in comic form, yet the plot is still pretty solid.