Gearbox & 2K Games have announced that the digital version for Borderlands 2 for PlayStation Network will be available the same day that the retail version will be, 9/18/12. So if you're PS3 owner and prefer a digital version, you won't have to wait it appears.
Source: GameTrailersLabels: Borderlands, Borderlands 2, Consoles, Digital Downloads, News, PlayStation, PlayStation 3, Playstation Network, PS3, PS3 Podcast News, Release Dates