Gotham Knights Could Have 4-Player Co-Op According To PSN Listing - Game Informer

The description for the game still mentions co-op with up to one other player, though.

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Gotham Knights Will Get 4-Player Co-Op In November

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Gotham Knights is Getting a Four-Player Co-Op Mode in November

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Gotham Knights will get a new 4-player co-op mode after launch