I think Square Enix already has enough reputation to be indecisive in their release date for Final Fantasy 15. Honestly, after Final Fantasy X, they’ve been hammering down more numbers like crazy. Maybe they don’t want to rush the game to where the story starts becoming bleak, and making people create wildcards to shun down the game.
The thing with Final Fantasy X is that it aimed to focus more on character development within the team you play with. Most of the other games in the RPG genre make the whole friendship and gregarious nature over-dramatized and pretty generic. And what makes Final Fantasy X different is that when the main character and Yuna interacted with each other, you could see how the game made it obvious that they would become extremely attached to each other. The story was linear, but it actually made sense and was easy to follow.
This isn’t to say all other FF games were inconsistent, it’s just that the narrative and character development hits home to me. But that’s just me, because if you have engaging characters, but generic JRPG stylized gameplay, I’ll still love it.