Let's start rumouring! What book do you think would be the last battletome of the edition? It could be a new faction, a second versión of a first year book or it could be FeC.
We can check 40k where the last three books were Votann, Astra and World Eaters.
Or AoS 2.0 were Slaanesh, Lumineth and Soulblight.