November for JP, December for the US is my bet. I was also think a simultaneous release for December was a possibility, but I think this #FE announcement makes that unlikely.
It's the day after Christmas though. P5 could release in both territories towards the top of December.
I don't know people said the same thing about the release of Smash Bros and Pokemon simultaneously and with the different user bases and different console bases, both games sold well as if there was no issue.
Nintendo has done their own thing for a while and they'd be confident enough in their product to launch it concurrently.
I honestly have no idea where else P5 will release. Last week of November at the earliest. An announcement next week with ~8 weeks to advertise and promote and what not makes it a very cramped situation.
It's weirder because most Persona games have sold in the Summer with Ultimax being the exception.
Promotion and marketing doesn't stop at launch though. Especially with a game like Persona. All Atlus USA really does is the usual YT clips/trailers and their newsletter. It's word of mouth that really carries these games and of course that comes from people playing them.
P4G made it to 700k because it was
the Vita game to own, that's what everyone would tell you (and probably still would) and it did (and still does) go on sale quite often.
I'd argue the ~8 weeks pre-launch are actually the least important. The enthusiast crowd knows. They're chomping at the bit. What's really important is what follows. The reviews (because casuals browse IGN and Kotaku, even if you don't) and the general word of mouth.
And streams wrt the PS4 port. That'll sell a few copies to the generation of Twitch Tweens, too.