This is not set in stone so don't take it as a planned feature yet, but my goal is to completely merge The Retreat with the other slaves after the new house revamp goes live. The MC can build workshops, training facilities, brothels, taverns, etc, (within his expandable yard) where his slaves can be appointed as workers. Going from an old 0.8.2 save to 0.8.3 would be seamless in that case; your retreat slaves suddenly just deciding to move over to their owner.
In addition to "the merge", I hope to get another seven active slots into the game and/or the possibility to release story slaves and have them as interactable (and "retake-able") slaves on the adventure map, kinda like how NPCs work. Michelle goes back to her apartment, Mai-Lynn stays with her father, Lovisa enters Mrs. Tillingast's household as a maid and Dakota heads back to Aimee's store.