My bet is still on Gamescom or PGW, but the more I think about it, the more plausible I find it that they keep the spotlight on their VR headset for the rest of the year, and release the Neo somewhere at the end of the year, or even somewhere at the start of next year.
I don't think they're aiming for a wide adoption with the Neo, but rather to broaden their audience by introducing hardware for the upper crust of consumers, while probably lowering the price on the base model for the lower crust of consumer. As such, I think it would be plausible that they release this thing as low-key as is possible, and just let it pick up steam on its own. They're obviously interested in it doing well financially, but I don't think they're as reliant on adoption as they were with the base PS4 model at launch (which should be obvious).
So, PSVR during the holiday, seeing as that's when you'll capture the biggest mainstream audience. And the Neo at the tail end of December, beginning of next year, seeing as the people it's aimed at would buy hardware at whatever point in the year.