Kiora Atua may be in one of the latter Theros sets as a planeswalker card. Her name even translates to involve gods and the monstrous mechanic for sea creatures seems to fit with her theme. I can kinda imagine she'd get an emblem with something like, "Blue creatures you control gain monstrous 2 for
."
I also suspect that Born of the Gods will feature a version of Xenagos with the transform mechanic, like
Garruk Relentless, who transforms from a planeswalker to a god card, and the final Theros set will feature a powerful God Card version of Xenagos who removes all gods from play when becomes a creature, based on the set pictures and lore hinted at.
Also predicting:
A Satyr with a lotus theme that basically grants the user mana and taps another target creature at the same time (sharing the lotus drugs). Something like Satyr Lotus Dealer or something, probably green/blue or green/red.
A card with an Achilles mechanic (a weird indestructibility with a loophole).
A Heracules based card as a Heliod related hero or lesser god, probably as white/red, which has high power and benefits in some way from killing monstrous creatures.
A Helen of Troy based card that forces creatures to attack or something, or has a similar mechanic to the Akroan horse where she is given to the opponent when she enters the battlefield and then benefits you, or something related to her famous beauty, perhaps making it so that god cards can't become creatures while she is on the field?
An Odysseus based card, probably a legendary blue colored one with protection from red, who has some kind of leader effect.
A
fleecemane lion pelt artifact equipment that grants indestructible or something to it's bearer.
A Rod of Asclepius based artifact equipment or snake creature that has something to do with healing or curing or preventing poison and/or disease.