I watched several interviews lately and while I don't remember which one it is, Jim said that in the aftermath of BG, it wasn't really the time for Harry to disappear into another time-line. So the next book won't be Mirror Mirror, it will be one that follows Harry over the course of a year, dealing with the changes that BG brought about. Including 12 dates with Laura...
I haven't seen anything on his website yet. Did anyone else catch this or see confirmation of it?