The Last of Us will not have co-op in the main campaign
It is rumored that The Last of Us will not come with co-op for the campaign which is a bummer and currently there are not plans for it. So mainly you will be playing as Joel throughout the entire campaign and Ellie will be following you along in all the levels doing her small part by assisting you through the entire gameplay. Stay tune for more news and rumors. Let's hope that even a DLC for this game might have co-op.