I don't see a 3rd faction coming any time, or honestly ever.. But you are right about being more like DAoC and less like WAR, and that being the rewards for the open world PvP.
Warhammer rewarded the individual... People just wanted their next piece of epic loot, and used the most efficient way to get it. Trading wins
DAoC rewarded the faction with bonuses, and a dungeon. People wanted these, and would defend the keeps to keep it.
You have the right idea, but they stated
"PvPvE balanced - bolstering the underdog faction through NPCs, turrets, etc. Factions claim objectives."
NPCs could be more than just defenders for your base. They can be a 3rd faction like in Aion that helps to regulate open world RvR. That is what I want to see along with what you said.