We have this WOJ:
The first quote is the main one that is relevant. I included the others from this link made by Serack http://www.jimbutcheronline.com/bb/index.php/topic,48717.msg2258880.html#msg2258880.
My main theory Murphy/Mab requires that Murphy revisit this time. That said, this thread asks the question if we will see from Harry's point of view in a time traveling book the events when both Queens died. Jim mentions these events in WOJ, but the avg reader really has no knowledge of this. So for it to be germane to the story other than mere backstory not in the books, Jim will need to write it in. How does Jim tie it into the plot? Will we get a reveal of who Mab and Titania are prior to ascending.
I think that we will learn about it, but that there won't be a time travel book at all, let alone back to this time period. I think that there may be some limited time travel, but that it'll either be for a very, very specific goal, or that Harry will get stranded in time around Proven Guilty, and he'll have to figure out a way to get back.
As for learning about Hastings and such, I think Odin will provide the exposition; I doubt we'll see it unfold on the page. You're talking about major, major butterfly effect stuff when you go that far back; Harry kills a guy, and his entire lineage for a thousand years is wiped out. These are the tops of a lot of family trees, including mine (my furthest traced ancestry is to the Domesday Book, circa 1086, and there is virtually no trace of birth or baptismal records that survive today beyond that). We're talking thousands of people over 30-40 generations. Considering Harry often leaves a body count, he could totally reshape history just by virtue of being himself.
Maybe he'll receive some kind of vision, or will get a Bob-theater movie, or some such thing, but I highly doubt Harry will ever go back that far.