Yes at long last news looks to be coming. A commercial on Nick for a special week next week where every day they will have a look behind the scenes at Nick's animation studio, including looks at upcoming shows including Korra.
In this advert for the event we do get to see around 2 seconds or so of footage. But it is an excellent sign that we may get a clip or trailer next week.
Here is a screenshot of Korra and the link to the video, http://moveslikekorra.tumblr.com/post/52513024237
