This will be on Serebii, Bulbagarden, and across twitter in the next fifteen to thirty minutes after the new trailer gets released.

Alolan Forms & Surprisingly a few new Megas (currently known) -
Bagon
Wailmer
Froslass
Girafarig
Swablu
Shinx
Munna
Scraggy
Minccino
Skarmory
Skitty
Feebas(Milotic Mega + Alolan, impacts Mega + new specific Z-move)
Riolu (impacts mega) (new specific Z-move)
Bunnerary (impacts Mega) (new specific z-move)
Charmander (impacts Mega) (new specific Z-move)
Flygon (Get's Mega also, and impacts Mega) (new specific z-move)
Ralts (impacts Mega) (new specific z-move)
Castform (not really Alolan, just a new weather patterns) (adaptive new & old z-moves)
Diance (jewel of the islands) (impacts Mega) (specific new Z-move)

Jirachi (specific new Z-move)
Celebi (specific new Z-move)
Rockruff (new form (fusion capable with Necrozma) (specific new Z-move, Theta)

New Forms-
Tapes'
Genies' (Alolan variants of Non/Therian)
Legendaries
+
Promotions with Pokemon Go-
Tanabata Festival (Fall/Winter)
Jirachi
Celebi

Rotations(Pokemon Go)
Japan to receive-
Ho-Oh
Raikou
Entei
Suicuine

Rest of the World-
Lugia
Articuno
Moltres
Zapdos

After Zapdos/Raikou
The tables switch/flip.
Legendaries will rotate for the Countries so everyone has the option to capture.

Exclusives-
Japan Only - Jirachi (for the moment, and the beginning of Gen 3)
Celebi (until next Spring)

2018 Summer -
Europe Only: Rayquaza
America Only: Mewtwo
Japan Only: Mew
2018 Spring - Gen 3 + PVP
2017 - Fall - Safari Zones (Malls/Shopping Centers World Wide, Regionals/Rares)
2017 - Winter (Christmas)
Smeargle + Delibird are released
Gen 3 Babies (Delibird event/Presents)