I wish I could tell you that I had some spoilers that I would post in another thread but Jim was pretty tight lipped about Peace Talks, but he did have some interesting things to say. Unfortunately, the audio on my cell phone video decided to crap out on me, so I don't have any video to post on YouTube, but that doesn't matter very much because I can give you the relevant information in this post.
Jim made a comment, which may have been a joke, that he had finished Peace Talks on Wednesday night. He said this during the opening ceremonies of the Con on July 4. However, he wasn't joking this morning when he said he will be starting to write the next Cinder Spires in two weeks. So I think it's safe to assume Peace Talks is all but wrapped up.
(This next part isn't specifically about the Dresden Files, but it strongly relates to future Dresden books.) When asked about how he's challenging himself to be a better writer; because Jim had just told an audience member that a writer should always try to do just a little more than they are already comfortable doing in order to improve, Jim said a recent rereading of The Aeronaut's Windlass felt to him like he had been a kid playing with action figures who smashed them together multiple times in order to have fun. He wants to tell The Olympian Affair; the next Cinder Spires book, in a smoother and more compact style than he's accomplished before. He said the same thing applies to future Dresden books. The word count on Peace Talks is 211,000 words, and that number could still go up a little further. (I assume he meant through rewriting a scene here and there.) He wants future Dresden Files novels to be shorter.
(More writing stuff, but again relevant to future Dresden Files.) Jim said that he didn't realize how much losing his dog Frost had hurt his writing ability. He said it wasn't until he had a new dog and the cats that sit around him when he writes that his word count started to rise from 250 words a day after Frost died to about 4,000 words a day he can currently do.
(Finally, something specific about Peace Talks.) In a panel Friday afternoon about writing combat scenes, Jim said the best combat scene he's ever written may be the one he just finished for Peace Talks. He said "Peace Talks gets apocalyptic; with a small a."
Jim had a couple more more things to say, but they were specifically about the Cinder Spires books, so I'll post them in that section of the forum.