Yes the new characters, and of course the ones IMDB posted up with no source (meaning they have not been confirmed yet)
Ikki- Darcy Rose Byrnes
Pema- Maria Bamford
Korra and Tenzin we have known a bit a bout for a while, but the rest are very interesting, the names especially, some of them are very asian (Japanese maybe) more than usual, Jinora, Hiroshi, Asami
They may all be related in the show, a family perhaps given the similar style of name.
Lieutenant may be the villain of Korra, Lance Hendrickson does a great bad guy voice (Lockdown in Transformers Animated)
Mako also a japanese name, and most likely another tribute to the Great Mako who voiced Iroh, David Faustino mentioned in a interview that Mako is Tall and Handsome, perhaps a love interest of Korra or Asami maybe.
I am so excited about Seychelle Gabrielle Voicing a Character, simply because I am glad to see that Mike an Bryan are not completely avoiding the movie. She was awesome as Yue so I think she will be great.
One thing to mention also is that this is a pretty big cast for a 26 episode show, even more given that most of these people are most likely in the first 12 so there may be more to come, I know some of these may only be one shot or minor characters, but it seems weird to announce bit part character voices as one of the few big info dumps we have gotten.
Not to mention, Meelo;s VA has not been named, the rumored Wei Bei has not been confirmed, Dee Bradley Bakers human character has not been named nor Dante Basco’s or Richard Epcars.