It could be that a personal or family matter caused the initial delay in finishing off the last chapter. It's also possible that the beta readers caught something that Jim had to go back and fix and the last chapter simply couldn't be finished until the fix was made, and now the past two weeks have been taken up with visits to far flung Cons.
I know Dragon Con; which Jim will be attending, isn't until the last weekend of August, so hopefully Jim can finally knock out the last chapter of Peace Talks, and anything else that may be required, and do so in the next few days. Jim said at Westercon that he writes five days (actually he writes at night) a week, so perhaps he's writing as I type this out. I hope he finish off Peace Talks in the next couple of days. I won't know what to think if it's not finished by the end of the week.