To be fair, given how long this has been in production, as well as the various comments made by Hashino about polishing vs adding new features regarding delays, if they've committed to September for Japan, at this point I'd imagine they're close to complete to the point of not vastly changing a majority of the game - of which localization could likely then at least start.
I'd imagine localization would be happening at this point, and 6-7 months til November/December isn't terrible.
To be fair, even assuming that, the other big issue would be if Atlus wants to try and go up against the AAA holiday release scheduling.