According to an interview with head of Final Fantasy XV project, Hajime Tabata, the game will only be half open world. Moreover, it’ll be the first half that is open world.
I had fears that his word choice or answering the questions in the interview may have hurt game sales and hopes. However, if he had not answered, or been too political, would people have been disappointed and claim to have been misled? Imagine the Final Fantasy fanbase then. A double edged sword.
(That way,) you won’t get bored of an open-world as the rest of the game gets tightened up, so we made it in a way that you’ll also get to advance through it as you have in conventional Final Fantasy games.
Moreover, by the time you get to Disc 3 in most Final Fantasies, it’s mainly linear anyway. Part of the convenience of classic Final Fantasies is not getting lost easily actually.