Well that was fast. *Update* · 10:38pm Jun 10th, 2014
So some spoilers from Amy Keating Roger's new book about Celestia and Luna are floating about, and it's not looking good for Though Ice and Shadow.
Journal of the Two Sisters spoilers ahead
Beyond having to change Crystal's name, a few things regarding the Empire's founding, and mentioning a scene about a dragon--I'm sure I'm still going to have to do some extensive rewrites if I want to keep the story somewhat canon.
The timing of this couldn't have been worse. I had just finished hammering out the last few holes in the story and had just started a Twilight Sparkle one shot.
Needless to say this kinda has me bummed.
Oh well, the silver lining is that it's now Crystal did exist and Luna/Celestia did know her. I just hope Amy didn't go over the Empire's fall, then I would have a real pickle on my hands.
*Update*
Got the relevant information from a friend, and Through Ice and Shadow has been rendered completely non canon. So I'm just going to pretend the book doesn't exist as far as my story is concerned. I'm not pleased to do so, but there is no way I can reconcile the two stories.
I've read a few spoliers and I already know that I will have to ignore it to make my headcanon work. I don't think there is much that I can salvage from it
Meh, I say treat it as expanded universe similar to how the comics are handled.