Wow - After ten games in the series called Final Fantasy, they have actually determined to make a game a real sequel, rather than just another game with the same controls and feel, but an unrelated series of characters. I'm right in thinking this is a first, isn't it?
No, this is actually a brand new game. Its a direct sequel, not a modification.
And FF12 has been offline single-player from the beginning. They are incorporating online elements, like connectivity to an online guide and things like that, so it will pretty much be what FFX was originally supposed to be - offline single player game with connectivity features that expand the game but are not actually part of it.