Im confident that McCoy will die, because I fully expect Harry will need the Blackstaff before it is over. I dont know that it will happen in Peace Talks, but it would be a fitting time for it, and one hell of a pressure cooker.
I agree with you, for reasons I've stated on more than one occasion.
Do we know someone important to the main cast will die? Or just assuming.
One of the first things Jim said about Peace Talks was it will have a high degree of supernatural violence. Which; if you think about it, is kind of an odd statement because all the Dresden Files books have some degree of supernatural nastiness in them. You can go through it book by book; human hearts exploding out of chests, werewolves eviscerating people, vampires seducing and killing teenagers, Summer Knight only had one human victim, though he was murdered too, a curse that can cause a plague, more, nastier vampires enthralling and killing people, necromancers killing people at will and either stealing their bodies and wearing them like a suit of clothes, or using them to be part of a zombie army, and I could continue but you get the point.
So I think we can safely assume that in Peace Talks there will be some deaths on the good guys side as well bad guys, and as we continue to get nearer to the end of the series the likelihood increases one or more those deaths won't just be anonymous wardens or Senior Council members we've barely met before. For example, if Ancient Mai or Martha Liberty were to die in the next book; the death of one or both characters might be used to set up some interesting complications within the Council, but they wouldn't have much emotional impact for the readers, because we know so little of either character.
Other than Susan's death, the only other deaths that have hit close to home for Harry have been Kim Delaney's because his decision to withhold information from her may have contributed to her getting killed, and Detective Carmichael because he knew and respected him. Harry also felt bad about Linda Randall getting killed in Storm Front because he recognized similar patterns in her life to his own. However, again other than Susan, none of these people had a deep emotional connection to Harry. Now we know Harry's mother was murdered and it's a strong possibility that his father was too, but Harry didn't go through the first hand experience of losing a family member to violence, these are just things he's learned long after the fact. Finally, even though Susan's death was very traumatic for Harry, it didn't; at least in the short run, change the trajectory of Harry's life in any significant way, partly because Susan had been out of his life for years before the events in Changes. Afterwards Harry was still going to get shot, become the Winter Knight and start doing jobs for Mab, even if Susan had lived. Long term, of course, Harry has a daughter now.
So we are speculating someone close to Harry is likely to die in Peace Talks, but it seems like informed speculation to me; not just a WAG. To get back to why Ebenezer makes a good candidate; his death has the potential to cause both immediate and long-term complications for Harry, and they would be dangerous ones to boot.