Sisters of Battle is the one army in Warhammer 40k that has been left out in the cold for a long time. Even though fans of the Adepta Sororitas would settle for just about anything for their long lost army, it would take some dedication to really do the Sisters of Battle right. Plastics are just the beginning of what it would take.
However there has been some recent little glimpses of hope, showing that they have not been squatted, and that they will indeed someday get to see the tabletop again. The new book Shield of Baal: Leviathan is that recent hope, with background showing the Sisters of Battle engaged in the fight with the Tyranid invasion.
Today a quick response from Forgeworld to inquiries about the army is another small glimmer of hope, that perhaps 2015 will be the year Sisters of Battle make it back to the tabletop.
a response to a reader's questions from Forgeworld
Thanks for writing in to us, although I don’t have great news for you. While the Adepta Sororitas will no doubt get an update of their codex and miniatures at some point in the future, at this time we don’t know when this will be. However, please be aware that the details of future releases are a closely guarded secret at Games Workshop so new content may be in the works, but we don’t have any specific information yet.
Please keep the faith that they haven’t been forgotten about and their time will come one day!