Okay so after watching one of the AK gameplay trailers, the titular character makes an appearance and attacks Batman. Then he says "There is no savior..no more hope..no more Batman." Now there are a lot of theories going around on who it is, Jason Todd, Joker, Hush, or even Batman himself. However, what stood out to me, was the Knights' percular accent. I don't know about you guys but it sounded French to me. So I was thinking, what French character has ties to Batman..Henri Ducard, one of his trainers. Ducard was a mercenary, So he could be hired to take down his former student. Another theory, it may be Ducard's son, Morgan, who made an appearance as the villain Nobody, at the beginning of the New 52.

The creators have said that the Arkham Knight is an original character, but I guess they could just be referring to the persona, not necessarily the person under the hood.

Yeah but maybe Ducard's son can be that original character, they can just use a different version of the one used in the comics since that one was pretty recent, and isn't really well known. And technically, when it comes to the Arkham-verse, Ducard is a new character since he never appeared or was mentioned in any of the previous games.

Ducard's son was Nobody right? In Batman and Robin

@takeluutzen Yes, he was the villain of the first New 52 Batman story, and one of the strongest B&R stories ever.

@anjales: umm lol that quote right there isn't Arkham Knight. That's Scarecrow talking.

@thecowwasdelirious No, it was the Arkham Knight, he says this after he knocks out Batman, then stands over him, says the line then holds the gun to his head, then the screen goes to black and a gunshot is heard. This takes place at the very end of the trailer. Scarecrow speaks in the beginning, he says the following: "Gotham, abandon this city, or I will unleash your greatest fears. Batman will watch as his beloved Gotham falls, and a city of fear rises." That is Scarecrow's only line in that trailer.

I'm sorry to destroy your theories but Rocksteady has said that Arkham Knight is entirely a new character just created for this game.

http://comicsalliance.com/batman-arkham-knight-main-villain-revealed-images/