It won't happen guys. There is a distinct formula to the Disney Princess line. Moana, Elsa, and Anna are not part of this line for reasons. The purpose of the line as quoted previously by Perm, is to sell merchandise. It was conceived when Disney Leadership saw young fans dressing in their own makeshift dresses to see their favorite princesses, so selling the outfit is essential. Other than that, you need to be a female leader (or daughter of a leader) with a cute animal side kick. Ironically, this criteria is laid out in Moana by Maui, but Moana will never be a "Disney Princess" because her outfit is based off of traditional Pacific Islander garb, and they already got in hot water for trying to sell outfits from the movie a a move of 'cultural appropriation' and insensitivity. So they can't add her to the line intended specifically to sell merchandise and dresses.
Elsa and Anna are not part of it because the lineup is already 'white washed' so to speak and they want to diversify the princesses as much as possible to broaden the appeal to all people. And since Anya/Anastasia is also 'white' along with originally being a non-Disney property, it just won't happen.
Leia doesn't have a cute side-kick, and they have also not added any live-action princesses to the group. Also, the risk of kids stumbling upon Bikini Leia may give Disney pause to giving her parity with the Disney Princess lineup.