There was a lot of noise about Sisters of Battle at Enter the Citadel. There’s some good news and some bad news.
The following was reported by a number of sources
According to Jervis Johnson “Every army (including Sisters of Battle) is getting worked on and will be updated in time.”
According to Phil Kelly, the reason why they never got plastic minis was because they couldn’t be plastic moulded by the current process. He also mentioned that there are 3 Citadel Designers who have full SoB armies as their main army. GW don’t intend to remove support for models that they have made
According to Jes Godwin. The sisters, like MkVIII power armour can’t be moulded from a 2 directional press mould. Even with all the computer aided design technology they have now. If the problematic detail and elements are removed or moved the models don’t meet the standards GW now have for their models. Jes wants GW to purchase better technology to overcome this problem, but the sales projects don’t justify it at the moment.
The indication is they aren’t in line for a codex soon. Phil Kelly has his hand up to doing it, but not until after Imperial Guard…
Other reports suggest the Sisters Codex did get some work done before 6th Edition but the army doesn’t function the way the studio need it to, even with any new units they had in line. So like the Dark Eldar they will have to wait another design cycle or until they are ready…
In short there are no time scales for the Sisters of battle codex, but the nail is not in the coffin yet.