Which Legendary do you think will be released tomorrow?

I'm guessing that it will be based on which team catches the most Pokémon during the challenge windows.

Mystic = Articuno Instinct = Zapdos Valor = Moltres

Mystic has won every "challenge" so far (after the events when they post such team caught the most Pokémon), so no reason to believe they won't this time also, most of the players are on Mystic. So if bet on Articuno.

Edit (Quote from main article by Niantic): "If they manage to catch enough Pokémon during the Pokémon GO Fest Challenge Windows, the first Legendary Pokémon will be revealed in Grant Park. If the Trainers in Chicago succeed in defeating the Legendary Pokémon, that Pokémon will start appearing in Raid Battles around the world, after Pokémon GO Fest."

It says "that" Pokémon, which leads me to believe that only 1 will be revealed.

Edit2: I guess Multiples could be released, so the title should be "Legendary(s)," but Reddit doesn't let you edit titles.