His lottery pick?
November 21, 2019 is Thanksgiving Day, so I'm thinking no. Books don't get released that day. If the clue had led you to the answer of November 22, AKA Black Friday, then maybe I would think you were on to something. I don't think Jim can get a firm release date until after he turns the finished manuscript in and the publisher can look it over and determine a release date. Till then, anything else is just guesswork.
I'm surprised Jim has taken so long to finish the denouement chapter. Normally he knocks those things out in two or three days. Seeing as how Harry is going to be kidnapped and sent to an alternate universe in the next book, I wonder if Jim would take a page from Quantum Leap and have that happen in the last chapter of Peace Talks with Harry suddenly appearing in the mirror mirror world as a mob of enemies closes in around him and saying the words in "Oh boy!"