This was a day or so ago, but nightfury in his comments on the site (he has had some particular good insight in the past) has mentioned the the moulds for the Adeptas Sororitas are done and production has started. This is a big deal, although it doesn't give us a release time frame. Done models can sit for quite some time in a warehouse, but it does give us a little more hope that we will see the Sister's of Battle sometime soon.
With the recent rumors from Bols that a summer campaign will include Sisters of Battle and Tzeentch, and nightfury's comments a release is looking very good for this summer.
please remember that these are rumors at this point.
via Nightfury on Faeit 212
I can guarantee plastic kits for adeptus sororitas will be released within the next 18 months.. the molds are finished and production is already underway :)
rumors from Bols a few days ago can be seen at this link
http://natfka.blogspot.com/2015/02/sisters-of-battle-and-tzeentch-releases.html