We do know how big this world is, though - we've got three major continents, basically: Aldenard (thats the one Eorzea is on), Isalbard and Othard (thats where we're heading). On top of that there are a few islands aswell as Meracydia (second large landmass) and The New World (third large landmass). Just because we dont see those ingame yet, doesnt mean they dont exists in the games lore.
Vanadiel, as you can see, isnt mentioned - and I dont want them to pull out a whole new continent all out of sudden.

FFXIV is FFXIV and FFXI is FFXI - I understand nostalgia, but the tradition of the series was always to keep the worlds seperated. I dont mind all those little refrences, I rather enjoy them! (even if I might not get all) But I'd rather have them create original content for this game instead of recylcing FFXI.