Sony announced that system software 2.0 will arrive on PS4 this fall. The firmware update will add a new feature known as Share Play, which allows PlayStation Plus members to invite any friend to play their games with them in a cooperative, pass-the-controller fashion. What's more, those that join their friends on Share Play don't need to own or download the game.
Update: PlayStation Blog
described Share Play as a "virtual couch," allowing users to play cooperatively together in addition to the aforementioned pass-the-controller method. The system update will also add a dedicated YouTube app and the ability to upload gameplay clips to the popular video platform, a feature Sony announced back at E3
in June. The What's New section of the console will also receive an upgrade with friend-of-friend suggestions and a real name search function.