Wow This Came out of Nowhere! While we aren't 100% sure this is the real thing, it looks way to good to be a fake, plus the voice sounds a whole lot like J.K. Simmons the voice behind Tenzin (Aang's son). Couple of things we noticed from the video
  • Title of the series is changed back to "Avatar: Legend of Korra" (Although this could have been made before it was named with The Last Airbender prefix)
  • Name of the first season is: "Book 1: Air - Welcome to Republic City"
Update - Sorry looks like series creator Mike DiMartino asked that the video not be re-posted. We can say though from what we saw Avatar The Legend of Korra looks way cool and amazing, no surprise there! Looks like things are shaping up for an awesome series. Source: Rufftoon's Deviant Art (I think he's a storyboard artist?)