From TLJ wiki:
Said at 03:17:00 twitch.tv livestream : Dag: "we never really expanded their story". Ragnar: "that will be continued in Dreamfall Chapters.." Dag: "yeah, they’re important", Ragnar: "because these things are very central to what’s happened here, yeah. They’re linked to some of the events that go on above ground. But I can promise you that you’ll not be FIGHTING any grubbers in Dreamfall Chapters!"
So it seems that Grubbers and Ancient City are more important for story of Dreamer Cycle than we think. The whole Dream Conspiracy can be releated to them. Necropolis. So maybe there is some ressurection plan? Maybe Dreams can makes some things alive? Maybe also Prophet is releated to Ancient City somehow?
Dream Chamber and blue prints for Tower are located in Ancient City.
Kian will play a major role in upcoming war...The Six and Emissary said that when Tower will be completed then Light Of Goddess will go across the world and clean it of evil - push everyone who lacks faith.
One of Dreamfall taglines: "The Future Holds Secrets Which Only Past Can Reveal"