They reveal the game has online multiplayer for 1-12 players, and online co-op for 1-3 players but they separately detail 'Number of Players' as 1-2.
This could very well mean campaign co-op is in the works at the studio, possibly letting a second player take the role of Nathan's good friend Sully? "1-3 Online Co-op, 1-12 Online Multiplayer".list Uncharted 3's game details as having
Under 'Number of Players' which is separate from all the online listings it states "1-2 Players" quite clearly. Uncharted 3: Drake's Deception has just received its first real glimpse of gameplay in the world debut trailer.