Single player co-op will be tied into story and cutscenes will reflect additional player.
Dead Space 3 is definitely in development according to IGN, who have been told on upcoming changes to the game
After a leaked video showed off Dead Space 3 being developed, more information from IGN reveals what the game will bring. A slew of details have been released, from new co-op support to changes in weapon behaviour.
During single-player, the character players can drop-in and out as has a scar on his face and an engineering RIG of his own. The character acts as Isaac’s guide, on a snow planet that was detailed last year. Event move from an engineering ship, as they take place around an unidentified facility. Sounds mysterious.
On drop-in and drop-out co-op specifically, Isaac’s story changes to accommodate the additional player. Most games don’t bother with co-op or explaining additional characters; the last game I played where additional characters were explained was Halo 3, where players could play as the Arbiter or one of two Elites that were named. Though Bungie didn’t acknowledge of explain the Elites in-game. An example scene given was the player and character stumbling out of a burnt wreckage, wounded and bloody. That scene only shows Isaac in single player.
Isaac also experiences hallucinations and traumatic events – something anyone would go through if an engineering ship was infected with psychotic deformed humans – but those won’t happen in co-op.
New weapons, powers
Players can also work together, using powers such as telekinesis to interact with the environment and undoubtedly solve puzzles. Player can share ammo and heal a co-op partner, though there’s no revive system. Both players reload at the last checkpoint once they’re dead.
Weapons and the Bench have also changed: weapons such as the Plasma Cutter are completely different. The weapon now has an alt-fire mode that has a knockback effect. IGN haven’t detailed how the workbench works, but I’m guessing it allows upgrades to alt-fire modes at least.
Isaac armor has been redesigned; it’s described as slender and and carried to the co-op character. Isaac can crouch, hide behind small objects. He also has a right/left evasive roll, which could be due to the open environment. I did like the restricted movement..