"The Legend of Korra takes place 70 years after the events of ‘Avatar: The Last Airbender’ and follows the adventures of the Avatar after Aang - a passionate, rebellious, and fearless teenaged girl from the Southern Water Tribe named Korra."
See, this actually bothers me a LOT because it means that Aang only lived to about 67 (technically 167, but you know what I mean). :( I had the impression that in Avatar world a life expectancy of 100+ is not at all uncommon; after all, Bumi was over 100 and still super fit, and Avatar Kyoshi lived to over 200. But even in our world 67 is way too young to die peacefully of old age! Which means he was probably killed by someone? At any rate, I don't like it.
But apart from that, everything else sounds super.
"Korra’s quest eventually leads her to Republic City - the epicenter of the world of “Avatar.” A metropolis powered by steampunk-type technology, the city is inhabited by people from all nations. Korra finds that Republic City suffers from rampant crime and is also dealing with an anti-bender revolt. Korra is tutored by Aang’s son, Tenzin, in the ways of airbending."
...Actually, this is starting to sound like Batman Beyond or something. O_o Looking at the image, it definitely looks like the Avatar version of New York (or maybe New Crobuzon). I really hope this doesn't mean they're abandoning the overarching story style of the first series for a more episodic, enemy-of-the-week style. Not that episodic can't be good; but for me part of what made the first series really unusual for an American animated show was that it followed a series-long, planned story arc with a beginning, middle, and end.
Anyway. Why do I sound so pessimistic? NEW AVATAR! :D