Far Cry 4's co-op is drop-in, not a separate mode
Far Cry 4 will allow players to team up more organically than in Far Cry 3's cordoned-off co-op mode.
According to a new PlayStation Blog post, a mode called Guns for Hire will allow two players to drop in and out of each other's games as they please.
Both players will receive experience and loot collected for their single-player progress, and can rampage across Kyrat as they please. It's not clear if this means you can do story missions together or not, unfortunately.
This feature is presumably available on all platforms.
There is a PlayStation exclusive, though. As previously detailed, you'll be able to share the game with PSN friends who don't yet own Far Cry 4, whether you have the PS3 or PS4 version.
Far Cry 4 is due in November. Want more? Check out the E3 trailer - actually the first five minutes of the game - and seven minutes of gameplay footage.