At its E3 press briefing, Sony confirmed that PlayStation 4 will require PlayStation Plus in order to play games online. This is similar to Microsoft’s current approach to online gaming with Xbox Live Gold. At the same time, Sony also confirmed that you’ll be able to play all single-player games as well as use all media services without subscribing to PS+. Your current PS3 membership will transfer over to PS4.
Additionally, Sony confirmed some upcoming additions to the Instant Game Collection will include Don’t Starve, Outlast, Secret Ponchos, and DriveClub PS Plus Edition.