Not as in resurrection, but in terms of a human scale Big-Bad. While we all know that ME3 will likely culminate in a huge space battle consisting of the Reapers against the collected forces of the galaxy, there has to be a foe that Shepard can fight personally. To use a (sloppy) Star Wars analogy, the Reapers are like giant, sentient Death Stars. Shepard needs a Darth Vader to fight while his allies have the big-space-battle-for-the-fate-of-the-galaxy outside. Saren fit this mold well, giving a face to evil that the Reapers simply cannot provide. He was someone to direct our hatred towards. The Reapers are faceless, giant, metal Space-Cthulhu, and it is more difficult to properly think of them as "The Bad Guys". The Collectors had more of a face than the Reapers. They were a face to hate. An enemy to fight. You can't fight a Reaper on foot. We need a "Vader", or a "Saren" that we can fight, face-to-face. An Embodiment Of Evil.
My suggestion? The Illusive Man. Why? Because in my view, it makes sense. TIM is obsessed with power, willing to do whatever it takes to further humanity, which, of course, means Cerberus. Allying with the Reapers seems like something he would do, if only to further his own goals. Perhaps he, as Saren before him, believed himself useful, or strong enough to resist indoctrination.
Well, that is my first wall of text on this forum, and if this was done before, well then I don't care. I tried searching, and nothing popped up, but then I think the thing bugged out on me. Please post your thoughts and all that good stuff. And please,
please don't hate me.