How about instead of falling out into the water it happened before they left the island.  Meaning it is still either on the Island and will cause a future problem or a squire found it.  As far as we know Harry has never checked to see if there are any coins on the island.

But think about it from the WC/Warden perspective.  DuMorne is dead.  This guy was a badass Warden:  he was in on the Kemmler finale!  And that was 40 years ago... presumably he's only honed his art further.

Do they believe that a punk teenager beat DuMorne in a duel?

A punk teenager who was under supervision by DuMorne, without much opportunity to learn/practice black magic?  And presumably without resources (books/etc) as DuMorne would have controlled such things.

From the WC/Warden POV, this premise seems absurd, a non-starter.  In their shoes, I would presume another party, a 2nd wizard; even if Harry was the proximate killer, who was pulling Harry's strings?

If DuMorne could be killed -- a top-tier combat wizard -- then nobody is safe.  That (presumed) 2nd wizard must be discovered, or be proven (beyond reasonable doubt) to not exist.

And it's that investigation -- of the grounds where DuMorne lived, of the mundane records such as school enrollment, etc etc etc. -- where I think Elaine's existence would have come to light, whether Harry tried to conceal it, or not... or was never even questioned on the matter.

I do not think anyone would be looking for another wizard. I think there were probably 2 groups those who trusted McCoy completely and those who just figured Harry took DuMorne by surprise.  Dumorne happily giving Harry a lesson.  Harry draws in lots of power to, Dumorne thinks, cast the practice spell.  Suddenly fire coming right at Dumorne and he does not get shield up in time. 

That group probably figured it would happen again with McCoy.  Either McCoy would kill Harry or if Harry pulled it off again they would kill Harry afterwards and would not have the annoying McCoy around anymore. 

Maybe; well, no -- not before the next novel.  But will a DF tv-series beat Jim to the end of the DF story, before Jim writes the novels?  Very very possible!

Peace Talks is #16.  We have 5ish more DF novels, then the BAT.  I don't really see a 1-hr episode being adequate for a novel.  I also don't see a whole SEASON for a novel.  Maybe... 3ish novels per season?  Not sure.  Depends in part on whether the showrunner (or whoever's making the call) wants every episode to end on a cliffhanger, how MUCH of the novels they include, etc.  Maybe they'd be willing to fit it into a variable schedule?  This novel gets 3 episodes, that novel gets 5 episodes, etc etc etc...

But the existing DF corpus should be good for enough time for Jim to get out at least 2-3 of the remaining pre-BAT novels.

Before Jim's RL blew up, he was churning out a book a year, basically.  His newest books are getting bigger, presumably it will take him a bit longer to complete them... 15 months each? 

He's alternating now between DF/CS novels.  So, a new DF book every 2.5 years, which makes it 12ish years 'til the BAT.

If he kept up the novel-a-year pace, it'd be 10ish years 'til the BAT.

While a show could do multiple novels a season they might also easily stick with just one novel a season.  They would just pad things with monster of the week episodes.  I actually hope they would never do more then 2 novels in a season as I would never want them rushing a novel. At one novel a season it would also take them a long time to catch up to the books. 

Do we know if Peace Talks is going to be crash-published or are we looking at the usual 6-8-12 months to publish after the manuscript is finished?

Just guessing but my bet would be they will get it out for the Christmas shopping season if they can.  If that requires a rush they will otherwise probably not.  As long as it is done soon enough for that to be possible I think we will get as much of a rush as needed to make that happen.  After that window completely closes I am not sure they would have a reason to rush anymore. 

I do not find it hard to believe that Hecate could have grown greatly in power while so many more major old gods faded away.  We know that belief has a lot of power.  People stopped believing in Zeus so he faded.  Maybe Hecate had an advantage in that all she needed was for people to believe in magic not her directly for her to gain in power or it could be that wizards know she was around and respected her more then the other old gods and it was enough for her power to continue to grow as all the others faded.       

New Theory:

Jim has just thought of an amazingly-kewl crossover, the Cinder Codex.

He has put aside the Peace Talks draft to write Vol.1 of this new series.

(this Public Service Announcement is sponsored by the Society for the Infliction of Cruelty to DF Fans)

Turns out it all takes place in a very distant part of the Nevernever, Furies are just not very smart neutral fairy that like humans and cats are all distant relatives of Cat Sidhe. 

Maybe Jim realized he needed to make a critical change back in Chapter 13, and has to re-work the rest of it going forward.

(this Public Service Announcement is sponsored by the Society for the Infliction of Cruelty to DF Fans)

Thankfully Harry is not one of the readers of the books because if he was Jim would probably be doing just that to torture him.

Time to break up the boredom and make a prediction.  It's been 11 days since it was announced that Jim was up to chapter 60.  I don't know if that means Jim is working on chapter 60 or he has finished 60 chapters.  That wording is a little vague.  Whoever is writing those updates needs to write more clearly; and I say that as someone who often needs to remind myself to write more clearly, but I digress.

For the past few weeks Jim has been knocking out a chapter every 4 or 5 days.  Several months earlier Jim was averaging about 8 days per chapter.  Now there could be some simple explanation why the current chapter is taking so long for Jim to get through.  Jim may have had some personal or family issue come up that he needed to take a few days off to deal with.  However, I'm hoping it's not an outside problem, I'm hoping it's actually a good thing; something indicative that Jim is really in the very final stretch of finishing up Peace Talks.  I'm thinking Jim has been working through all the final twists and turns of the final confrontation or set of confrontations Harry must pass through, and following the conclusion of the current chapter (or two) there will only be the epilogue to write.  The epilogue chapter probably won't take more than 3 days for Jim to knock out.

Even if the current chapter isn't the penultimate one, the extra time Jim is taking to finish the current chapter will mean the final boss battle chapter will go pretty quickly because Jim has already set everything up for the conclusion he's aiming for.  I think after the current chapter is finished, it might only be 3 to 8 more days before Jim writes "The End."

The problem with you idea is that we do not always get an update for every chapter.  This means that while you could be correct and the latest chapter is taking a little longer it is also possible the next update will say chapter 62 or 63 not 61 meaning the chapter is not taking any extra time compared to others. 

It is also possible we will just get a book complete notice soon and we will not know for sure how many chapters until we get the book.