@Skydragon0 My money's on that horny brat Kiana, already because unlike Kallen she didn't already get her girl (re: the Sakura Samsara sidestory)... :d
Though when you think about it this gets pretty meta levels of gay as Sakura moves around outside her little pocket netherworld by borrowing Mei's body and presumably something similar is the case between Kiana and Kallen as the latter has been equally physically dead for the last five centuries (and not coincidentally uses the same Awakened Soul mechanics)...
Some echoes of the finale of Kindred Spirits there come think of it, actually.