Agents of the Imperium is going to be an interesting book. I will my Inquisitorial updates which is always nice ( I miss those models dearly), and above all else... Sisters are included.
The White Dwarf revealed all of this for December releases.
White dwarf confirms sisters of battle in imperial agents codex, aswell as
8 other factions (listed ones are inquisiton, adeptus astra telepathica,
assassins, deathwatch, and GREY KNIGHTS :-)) guess unlisted ones are
custodes, sisters of silence and one more. The quote is
"within this volume you will find background and rules for using 9 smaller factions, alongside
your existing armies of the imperium, from the grey knights terminator squads to the battle sisters of the adepta sororitas"