There hasn't really been much of a pattern to the reveals.
I would say there has been, in regards to character status and relationships.
Sophitia and Mitsurugi - "Poster" characters, one female and one male, who have been with the franchise from the beginning, even SoulBlade.
Kilik and Xianghua - They're inseparable, really goes without saying.
Kilik and Grøh - They're rivals, if Vergeben is to be believed.
Xianghua and Nightmare - The hero and villain of SoulCalibur I-II.
Zasalamel and Ivy - "Magician" type characters on either side of the Soul Edge situation. Notably, both appeared on the cover to SoulCalibur III.
Maxi is a missing link to the trio of himself, Kilik, and Xianghua, so he could be next for that reason, and Taki has ties to Sophitia, but Talim doesn't fit in so much. Talim is mostly tied to Yun-seong and Seong Mi-na, characters-wise, though there is the central idea that she'd be linked to Nightmare, to oppose Soul Edge, but that was practically everyone in SoulCalibur II, who each had fragments of Soul Edge that led them to Nightmare. And then there's that Maxi probably can't be introduced without Astaroth, as their souls are fiercely entangled.
So if there's three, it seems more likely to be Maxi, Astaroth, and Taki.