To get back to the OP. Because of the amount of time since the last book, I; make that we, have had a long time to think about Peace Talks. I; and probably a few of you out there, have thought this book could be the right time and place for Harry to permanently lose his mentor. It's not that we want to see Ebenezer die, but the basic structure of the Hero's cycle is that at some point the mentor character leaves the scene; usually feet first, leaving the hero to stand on their own.
Of course, the risk of doing something expected (predictable) is that the writer's work can start to look stale and unimaginative. So I'm thinking something else might be about to happen. Something that makes Harry stand out to the rest of the White Council, but doesn't necessarily kill off Eb. Plus, Jim has said he prefers to torture his characters, as opposed to just killing them outright.
So re-reading that scene with Ebenezer and Harry, I was taken with the phrase, "the most feared wizard on the planet." Ebenezer is feared because he wields the Blackstaff. Perhaps not every potential supernatural enemy is as well informed as Kincaid is on this fact, but I bet every potential supernatural enemy knows that Ebenezer McCoy can do some extremely scary stuff. So we see Eb's hands are trembling from the psychic attack he is undergoing. Harry also felt this attack, but he fought it down and is in better control of himself. Now add to this something from way back, the last conversation Harry had with Lash just before she took a psychic bullet for him. She told Harry he had "the potential to wield power over Outsiders." Well so far that power has allowed Harry to recover from and resist Outsider mental attacks and trash talk one of the Walkers, HWWBf. Oh, and Harry's name is now some kind of a weapon. It's impressive that Harry can stand up to Outsiders, but it's not my idea of how a wizard would "wield power over Outsiders." I believe there's got to be more to what Harry can do to or with Outsiders that he hasn't discovered yet.
Remember Lucio's reaction when she saw Zombie Sue. She was impressed but there was more than a little revulsion in her reaction as well. So imagine the reaction of the Senior Council if Harry publicly demonstrates some of this hidden power over Outsiders. Depending on how it plays out, I could see a reaction going something like this; "Yea! You've saved us. Holy crap, did you see what Dresden did? Dear God, what if he aimed that power at us?" As usual, the White Council will misinterpret what they see. They; and probably a good chuck of the supernatural community, will begin to see Harry Dresden as the most feared wizard on the planet. They thought Harry was scary when he wiped out the Red Court and came seemingly back from the dead, so now they will see something that scares them even more. So even if Eb doesn't die in Peace Talks, even with the Blackstaff he won't be able to produce the results that Harry does. So a kind of changing of the guard occurs, no matter what Eb's fate is. Oh, something bad could still happen to Eb. Remember what I said about Jim torturing his characters, but I don't think he has to die in order for Harry to stand on his own.
On a totally unrelated matter. The Dresden Files being highlighted in Entertainment Weekly? I don't think that has ever happened before. Good for Jim that his work is getting a major push. Jim may be a best selling author, but I doubt his work puts up J.K. Rowling's numbers. A lot of people in the entertainment industry are looking for the next "Game of Thrones." (If we forget season 8 and a good chunk of season 7.) This could be a sign that someone; probably the people who purchased the TV rights to the DF's, are trying to give Jim's work a chance to be the material for that show.