At least, for what I understand in the Video, says that Eorzea is a Region, the director says
Nobuaki Komoto said:
Vana'diel as a full world, is naturally a little bigger. So Eorzea will be the name of the region that serves as the main setting of the game. We will be using a different name for the world itself, which is "Hai-de-rin".
I know for a fact that in Japanese language a lot of things are implied. I wonder if this means that this game is still set in Vana'diel, but being in another region, that other region calls it Haiderin. Would make a lot of sense.
The World of Vana'diel
You must join hands... once again.