[Asakura]

So we know so far that X, X-2 and VII are connected. X, and X-2 seem to be in-game historically older then VII.

Do we seperate Ivalice and the other worlds?

For example FFX takes place in Spira
FFVII's world is Midgar
FFXII's world is Ivalice

Are they all the same world, Just different times and names?
And do you have repeating technological history?

Or maby (and this is my speculation alone) Ivalice is a whole other planet, plane, demension, something like that. Of couse if you acknowledge that then you'd have to acknowledge the theory that they ALL are alternate demensions.