IIRC, Jim has mused in AMA events that a GG spinoff might be one option after the DF+BAT wraps up.

... As to the mirror swapping, Mirror Harry kills the new arrival Harrys to cover his tracks, so it's likely they will both be in the same universe ...

As I understand it -- I may be mistaken -- alt!Harry doesn't (or doesn't often) actually *kill* the other Harry's.  His M.O. is that (when he's utterly cornered and sees no way out) he summons an alt to die in his place, usually at the hands of whoever was going to kill him.

Then the Harry-killer knows for certain they  finally got the bastard!  only for Mirror!Harry to pop back up (a day or two later) and blindside them.

Dogs comprehend a lot more than you think, or the intelligent ones do. 

As a lifelong dog owner & sometimes trainer & avid reader about dogs, I'm aware they are smarter than most give them credit for.

For those who *don't* know -- the "average" dog seems to have a comprehension vocabulary of just under 100 words.

Working dogs usually top 200 words.

Ultra-intelligent ones have been documented to over 1000 words -- https://en.wikipedia.org/wiki/Chaser_(dog)

Also, in a recent video, his wife needs him to finish it before the new year I believe,  over a comment or discussion with a redditor? 

Welp, he looks unlikely to hit "by the new year!"   
It has been stuck at 28% complete for over a month.   

Maybe we can generously presume the timeframe was "a year" (i.e. from whenever the reddit exchange occurred) rather than a hard-dated "by new years."

In Changes, and subsequent stories, we learn Mouse is capable of communicating at a human intellect level. In the subsequent stories, we see that some humans can understand Mouse or other human level intellect canines (for example, Molly and the Alphas in Bombshells). When Harry is in dog form in Changes, Harry can understand Mouse:

Also in the first chapter of Changes, Harry seems to understand Mouse at that same intellectual level:

Harry could have been just guessing at what Mouse meant by interpreting his body language and stuff. I personally think Harry was dissociating enough that he was in a state where he could "hear" Mouse like Molly does.

Do you think Harry capable of understanding Mouse? I doubt he will ever understand Mouse in the books because, as Jim said, Mouse knows too much. My question is whether he could if he worked on it.

Harry has always talked aloud, to himself, as one of Jim's exposition techniques.

Dog-owners -- by and large -- talk to their dogs, in ways far beyond what dogs can comprehend; Jim used that as an expansion of Harry's own talk-aloud habit.

But it has been an ongoing theme of the stories that Harry has realized more and more that Mouse is far more intelligent than the average dog.  There's a scene in Turn Coat where Mouse gets shot (bullet didn't penetrate far) protecting Molly, and Harry uses it as a "teaching moment" to get Molly more aware of the potential consequences for her actions... and shortly thereafter, Harry realizes that Mouse was deliberately feigning a worse injury & more pain, playing to Harry's own lessons in perfect comprehension of what Harry was teaching, and how Harry was going about the lesson.

... the A.I. gave me this:
------------
<SNIP>
-----------------
This wasn't in the copy of Battleground that I read ...

Classic AI hallucination:  include a light dusting of genuine references, but placed in incorrect contexts for a surreal result.

... It was a warning, Harry took it as a warning, Harry was ashamed and didn't forget.  In other words a strong warning, and then Harry went on to try and redeem himself.  That's the point ...

No; the point is that Angels don't do that.

They do not "step in" that way, not even to "warn:"  not with an unambiguous Angelic-caliber "thou shalt not," not to influence mortals' free will.

That the Sword did burn Harry can only be a "warning" that a Spookyside "bad actor" is acting upon Harry; that his free will isn't entirely his own.  A free-willed mortal choice does not get an Angelic response or intervention.

... Or very realistic, between his adrenalin and the Winter Knight's mantle Harry wasn't going to come to his senses that easily or quickly after seeing his beloved murdered and bleeding out in his arms.

Hypothetically, the WK-mantle influence may indeed be sufficient to get a KotC/Angelic intervention.

...

Maybe...

But ...

1/ But also, nope -- Harry already made that choice, and now has to live with the consequences.  When he chose to take on the WK-mantle, Harry chose chose to eventually become a monster.  The Angels (once again) do not intervene/warn when mortals have made their choice.  You might argue that some mortal may have been "tricked" into taking up a Knight-mantle without understanding how it could mess with their head; but Harry knew it would happen, fully accepted that it would (as it turns out, he has a slim chance not to become a monster!).

2/ But also, why both(all) of the Knights?  We really don't see more than one KotC stepping into a fight for "just any" supernatural threat; and as "threats" go, a faerie Knight isn't exactly top-tier!  The most-obvious answer to "why are all the KotC's in that fight?" is "because they are fighting the KotC-archfoe, the Denarians."

= = =

I want to reiterate, here, that my "Denarian Hypothesis" here is actually my #2 choice, not my #1.

I think "it was just the WK-Mantle (with no Denarians) that triggered/enabled the Sword to act" is a better argument.  .. but also, I think there is a decent argument -- with supporting Dresdenverse lore -- to make a solid case for a Denarian Shadow to be involved.