While I'm happy to see a new Avatar series on TV in the near future (and that trailer was excellent, despite them using music from the 3rd season of the first series), I'm still a little wary of this series. The original concept was designed for a short miniseries, and for a miniseries the story was fine. But now it's expanded out into 26 episodes over 2 seasons, and I'm a little concerned there's not enough of a story here to be compelling for that long. Part of what made the first Avatar series so cool was watching Aang slowly master the elements as the year went on and the comet approached for the final showdown. But in this series, Korra already knows 3 of the 4 elements, so for all intents and purposes there's really nothing in the show that should even be able to touch her (especially since she knows Earthbending, which seems the most ridiculously powerful of the 4 bending styles judging by Toph). Where's the drama in a bending battle going to come from? And I didn't see any sign in the trailer that she had companions that traveled with her that gives the writers personalities to bounce off of her.
This series is coming from a very good pedigree, but I'm a little nervous that the concept they've revealed may be a bit too limited for essentially a 2-year show. And yeah, this show should proudly bear the "Avatar" title like its predecessor. The TV series had the name first, and it's not Nickelodeon's problem that James Cameron decided to remake Dances with Wolves with Smurfs and take the Avatar name as well.