Carrie Fisher was recently hospitalized for a bipolar episode, forcing her to cancel out as keynote speaker at a Florida fundraiser. Before that kerfuffle, though, she gave an interview to Palm Beacn Illustrated, who ran the interview even though Fisher's mom, Debbie Reynolds, replaced her as speaker. During the course of the talk the interviewer asked if she would be returning as Princess Leia in Star Wars Episode VII, and Fisher bluntly said "Yes."
The follow-up question: what is Princess Leia like now?
Elderly. She's in an intergalactic old folks' home [laughs]. I just think she would be just like she was before, only slower and less inclined to be up for the big battle.
This isn't exactly a surprise. As I mentioned when Mark Hamill confirmed his involvement, Disney has offered the actors a shit ton of money to return, and Fisher and Hamill certainly have no reason to turn that down. The question remains how involved these characters will be: will they be cameos, or will they have major roles in the new film?