What cultures/time periods will the game borrow from?

I saw a dev interview from a couple weeks ago where they said that they will not do anything past the 15th century, but what about backwards in time? I would love to wear a roman armor set and many others would love to wear armor from various different time periods and cultures like the vikings, samurai, spartans, etc. Is there going to be any possibility of these in the future or is it strictly Medieval Europe?