Okay, so far the only details we actually know of for the upcoming Citadel DLC are: -A conspiracy has been made against Shepard. -Miranda will make an appearance -Wrex will make an appearance -It will take place after the Cerberus coup attempt.
Now, I'm pretty sure whoever is behind the conspiracy is going to be an existing character, it'd be pretty pointless inventing some random character to fill the gap in a conspiracy storyline. This character must fit the following requirements:
- They must have motive, obviously.
- They must be alive under any circumstances, regardless of Shepard's previous choices.
- They cannot be anyone central to the plot (for obvious reasons), The Illusive Man, Anderson, Kai Leng, Joker, etc.
Now only one character actually comes to my mind at this point. Wreav. I know it sounds ridiculous, but hear me out. The announcement for the DLC specifically mentioned Wrex, but not Miranda, despite both appearing on the poster art. Secondly, regardless of the situation, Wreav is never confirmed to have died. If Wrex survived Mass Effect, Wreav is seemingly killed, but it is never confirmed, and a squad member will even comment that he could still be alive. Unlike Wrex, if Wreav is the clan leader, he never finds out about the sabotage if Shepard doesn't tell him, or does he? Now remember, this DLC only takes place after the cerberus coup attempt, which is incidentally the first time you are able to visit the citadel normally after Priority: Tuchanka.
Which brings me to motive. Now I believe Wreav would have a motive to conspire against Shepard regardless of whether or not he was the leader of the krogan, and regardless of whether or not the genophage was cured. In all of these situations, I believe he would have a reason to want Shepard out of the way. If Wrex is alive, then the krogan become much more civilized, and the traditional krogan ideals that Wreav believes in abandoned, well, if Wrex has anything to do with it at least. And who's responsible for Wrex being the krogan leader? Commander Shepard. Now let's say that you decided to kill Wrex on Virmire (you heartless piece of sh...), which means that Wreav is clan Urdnot's leader, and therefore, leader of the krogan. If the genophage is cured, to prevent any chance of peace with the salarians, Wreav refuses to acknowledge Mordin's/Paddok's sacrifice, and takes credit for the cure himself. But there is a flaw in that. Shepard knows, and Wreav just might want to stop Shepard from spreading that information, or worse, use it against him.
Well, that's my prediction and my reasoning behind it. Feel free to love/hate me for it. Preferably love, but I'll take what I can get.