Now that Theros has been announced and it appears to be heavily Greek influenced what can we expect design wise? Innistrad showed what top down design can do when it comes to mechanics and flavor, so we should be able to speculate what will be coming in Theros if we can think of ways Greek mythology can be put into a magic set. My basic stab in the dark.
There will be mythic gods and each will have their own equipment or blessings/favors/enchantments they can bestow upon normal creatures. We've seen metalcraft recently and battalion which focus on numbers and with the echantment subtheme in RTR I think we can see something similiar this time when you have three enchantments on the field.
I'd like to see city-states incorporated some way.
Lots of monsters like hydras, leviathans, chimeras, cyclopses, harpies, centaurs and minatours. Duh.
Is there any old mechanics they can bring back that would fit well in the set? They had flashback in INN and Imprint in SOM afterall.
With the third set being about Nix I think we are goind down to Hades/hell some way some how. Again, another duh.
We don't know much but I'm excitied. I've dreamt about how cool an ancient Greek set could be since I started playing. I wouldn't mind seeing bits of Rome or Egypt thrown in for good measure.