It seems that Warner Bros.

Montreal has decided to add 2 players to the Co-OP mode of the Gotham Knights game.
In fact, the title would go from 2 to 4 players, even if this feature seems obvious since the title announcement.
This information comes from a Reddit user who would have seen the title on the PS Store displaying Gotham Knights playable to network players.
Was it a Sony blunder?
The information has been replaced since, but hey, with the Summer Game Fest which may approach that Warner Bros Interactive plans to make the announcement during this event.
In short, it will be necessary to wait for a while before seeing if it is indeed a modification of the studio.

Gotham Knights Will Support 4 Player Co-Op Now?! - New PSN Update
So, what do you think ?