With WoD in a month, what do you feel will happen in to FF14's population?

[Avraym]

To my perception, you are forgetting about the player who is filling time with FFXIV. So what about the WoW player who does in fact only play WoW. However now that his character are level 90 and wearing the Raid equipment from MoP, this give him an opportunity to play another game until more serious obligations approach him again in WoW.

I didn't forget that. Like I said, many players left after Cata/MoP. A lot of which are currently FFXIV players.
If the expansion brings everything it promises, expect the players to follow.
Not to mention that by the time players have raids in full clear with the equip they need, the first major patch usually roll's around with more content.