The plot of Batman Arkham Knight was supposedly leaked on 4chan recently by someone claiming to have signed a non-disclosure agreement with Warner Bros. he was breaking by revealing details of the game.
That this alleged script was posted to 4chan should tell you all you need to know about its tenacity. However, let's break down some of the reasons why this script is not the real thing.
Firstly, the official Batman Arkham Knight Facebook page recently detailed Operation Saviour, which is the Arkham Knight's plan in the game. The leaked script makes no mention of Operation Saviour and one assume that given the fact the game is named after the Arkham Knight, his plan would be rather important.
There's also no explanation of why or how the Arkham Knight got his name, while it's possible that this information won't be revealed in the game, it seems far more likely that we'll know by the name the credits roll. Even if that information is being withheld for a DLC, you would imagine that there would be some hints around Gotham regarding the character's name.
In the leaked plot, it's said that the Arkham Knight is a clone of Bruce Wayne who created with an enhanced version of the titan formula to speed up his aging process. The Arkham Knight was allegedly created by Doctor Amanda Waller but the plot gives no explanation regarding the origins of his name.
The plot also makes no mention of Harley Quinn, Penguin, or Two Face.
Batman Arkham Knight has delayed until 2015 and may be set for release in February; regardless of when the game is coming out, it's slated for PC, PS4, and Xbox One.