Even though the premiere is a year away, I still have predictions. So, I'll start with the characters.
Tenzin: I think he'll have blue eyes and be bald with the airbender tattoos. However, I think because he'll be living in Republic City during an anti-bender revolt, his hair will be growing out. I think he'll be in his fifties and I would enjoy it if he wanted nothing to do with Korra a first.
Asami: I think she'll be an old friend of Korra's, helping her on her journey to first find Tenzin, and then to stop the anti-bender movement. I think she'll be carefree and wild, possibly Korra's foil. I think she'll have black/brown hair with light blue eyes.
Ikki: I think Ikki will be on the side of the anti-benders. I imagine Ikki will be an earthbender struggling to control his/her abilities. I think Ikki will have brown hair and green eyes.
Pema: I think she'll be Tenzin's non-bender sister. I think she'll have grey eyes and brown hair. I think she'll either be part of the anti-benders or be good and be closer with Sokka then with her own parents.
Mako: I think he'll be the grandchild of Zuko and Mai and the current fire lord. I think he'll be calm and serious, but have a sense of humour. I think he will have black hair and gold eyes.
Meelo: I think he could be the child of Hope and Tom-Tom. I think he'll be childlike, very out-there and strange. I think he will have brown eyes and brown hair.
Hiroshi Sato: I think he'll be a rich businessman who seems impartial to the revolts, but when pressed, will help the Avatar. Or he could be the leader of the anti-benders. I think he'll have dark eyes and hair.
Lieutenant: I think he'll be a scheming military officer who will do anything to work his way to the top.