been hearing Hush plays a MAJOR role in this game, so i'm going with him being under that mask
he probably will inpersonating bruce, not as the knight...
as for the knight, here's my theory:
like i mentioned in the game thread: i think it should be a split personality of bruce wayne....say scarecrow drugs him with some new shyt and a reaction to it is him becoming the knight....the knight can be all the surpressed emotions, thoughts, etc. from being the bat all these years....and the knight can be the 'batman' that goes all the way: breaks the law to get the job done and even kills the criminals cause he's tired of the 'lock them up to get out' cycle...he would be able to do everything batman can, have similar gadgets, etc. and bruce wouldnt recall doing any of the crimes cause it would be another personality...