November is a pretty poor date and I doubt SE are happy about it but it is what it is.
Here's why November isn't great: If you launch in September, you're competing with what's launching around you. FIFA, Mafia were FFs big rivals for this - plus Persona in Japan. If you launch in November there's far less around you, but that's not the issue any more.
The issue is that every other game has already launched (more or less) and so you're the last potential consideration for a casual user. If you launch in September, you have several months to catch a player who is just looking to pick something up in the winter busy period. Come November, if a player has bought Madden, Skyrim HD and Mafia 3, they're unlikely to buy another game.
So late in November is also a bad time for a broad-targeted release because a lot of people have significantly less disposable income at this time as they're shouldering the cost of the holiday season; presents, extra food, whatever else. In the US you also miss thanksgiving and black friday.
This is basically why in December you only typically see licensed games, 1st party releases designed to be a final push for the console sales as presents, and very niche games or remakes and the like.
So... it's not a great date, but it'll be up to SE to navigate that. If I were them I'd have been tempted to push out to February or March, but if you push there you're admittedly going to run into Horizon, Mass Effect etc.
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One thing I wonder is if this could impact KH 2.8; I could actually see KH2.8 getting pushed back as a result. One thing SE will have to do is now push fabrication and manufacture of FF15 discs back at the busiest time of the year for manufacture. If they can't find the capacity at the right price, they might commandeer space already booked: IE delay 2.8 since it doesn't yet have a firm date and use its allocated manufacture space for some of FF15.