It should be noted that if you live in a country where PS Direct is not available, then the system will be available to pre-order from participating retailers from 26th September. This period of pre-order exclusivity only applies to countries which have PS Direct, which includes the USA, UK, Germany, France, Belgium, the Netherlands, Luxembourg, and more.
Sony has been pushing consumers towards its own storefront more and more of late, so it's no surprise to see it make this move. It does mean that those looking for potential trade-in offers or other incentives may need to sit tight, though, potentially running the risk of supply running out. It's an unnecessary complication for a pre-order process that was otherwise looking relatively straightforward, but at least PlayStation has given us the heads up.