According to Todd Fisher, brother of the late Carrie Fisher, the unused footage of Leia Organa from Star Wars: The Force Awakens that will potentially be used in Star Wars: Episode IX is substantial and looks “like it was shot yesterday.”
During an interview on Good Morning America, Todd said that this footage is not simply outtakes or reshoots, but “new content that could be woven into the storyline.”
Source: IGN.com Star Wars: Episode IX: Carrie Fisher's Brother 'Thrilled' With Leia Footage