Rounding up the speculations. Bolded are pretty much confirmed. Others are guesses.
Speculations:
Gigi, Mica, Vittoria -- Chanel? Versace?
Gigi - Fendi ?
Mica - YSL?
Grace Cheng - Bottega Veneta?
Cara Delevigne, Lily Rose Depp -- Chanel?
Anna Mila Guyenz - Zuhair Murad
Sarah Brannon, Sarah Dahl, Atty Mitchell, Masha Skokova, Mariam de Vinzelle, Janaye Furman, Sora Choi, Rianne, Hoyeon Jung, Alexandra Micu, Theresa Hayes, Sophie Turner, Jaden Smith - Louis Vuitton
Cong He, Hiandra Martinez, Imari Karanja, Faretta - Coach
Aira Ferreira, Ellen Rosa, Fernanda Ly, Cara Taylor (+ Ruth) - Dior?
Kris Grikaite, Mia Brammer, Amanda Murphy, Vanessa Axente - Prada
Leila Goldkuhl, Julia Nobis, Lulu, Sara Grace, Blésnya Minher, Kiki, Jonas, Ernesto Cervantes, Khaleb, Salomon Diaz, Jared Manhardt and Fernando Albaladej - CK Jeans
Leila, Julia, Blesnya, Kaya Wilkins - CK mainline?
Anja - Anthony Vaccarello
Mckenna, Roos - Rag & Bone (campaign or e-commerce)
Maartje, Ine, Luna - ???