The product description on the GW webstore (Canadian version) says "A full army list for the Battle Sisters of the Adepta Sororitas". If it was just intended to "add thematic elements" to other armies, I would have expected something more like the GK, DW or AdMech sections, rather than a near complete reproduction of the Adepta Sororitas Codex, complete with Uriah Jacobus (but not Saint Celestine). The only positive possibility suggested by this is creating a physical book for the Sororitas rules that people are likely to own in the event a future supplement comes out with new stuff as with the Tau in Kauyon and Mont'ka, but to be blunt, I'll believe it when I see it, and it's easier to believe they cut Celestine because they're out of her model/were close to out at the time they were preparing the book and have a policy of not having options in codices that they don't produce miniatures for to prevent 3rd parties from stealing their thunder.
In any event, as the ebook codex doesn't format properly on my computer (something odd about the page length disagrees with my laptop's reading app) I suppose this qualifies as more useful than the ebook dex.