A few blog posts have been released detailing upcoming content.
Total War: WARHAMMER III – Introducing the Champions of ChaosGoing over the details of the upcoming Champions of Chaos DLC pack it explains the faction abilities of Azazel, though not the other 3 chaos lords coming yet, as well as the new units, campaign mechanics and regiments of renown.
One of the big things here is how Warriors of Chaos units can be upgraded. Starting from a base unit of Norscan Marauders you can dedicate them to a Chaos God or leave them Undivided, ungrading them to Chaos Warriors, then to Chosen or Chaos Knights as well as Aspiring Champions in some cases, then through to Chaos Spawns.
Heroes can also be dedicated to a single god, gaining access to new skills and abilities, such as a Chaos Sorcerer hero being dedicated to Slaanesh and choosing between the Lore of Slaanesh or Shadows, resetting their skill points and changing their appearance.
Total War: WARHAMMER III – Immortal Empires Race UpdatesThis blog post covers some of the most significant changes being made to existing factions in the Immortal Empires update. Including the Vampire Counts, Lizardmen, Dark Elves and Norsca.
Key for Vampire Counts is no more free skeletons research, but an increase in LD for all of their units as well as stat buffs for Etheral units and being able to recruit Mournguls if you own the Vampire Coast DLC. Raise Dead also provides better units earlier and seems to scale off of Vampire Count Corruption. Recruitment buildings have been reshuffled, tech tree gone over as well as skill trees and Bloodline effects.
For Lizardmen, Primal Instincts on Saurus now provides larger bonuses early as well as not having Rampage any more. Gor'rok has had his Unbreakable rite changed to providing a barrier to Saurus units and immunity to effects like poison.
Slann also gain barriers and changes to their magic trees. Nakai has some changes to help his economy and from constructing his Temples to the Old Ones, as well as benefiting from overall improvements to how vassals work.
Dark Elves have had how their Slavery mechanic works changed. Slaves now being a faction level resource that you spend at certain buildings to generate income or "invest in three powerful 'slave Diktats' to benefit a specific province".
Norsca can now colonise anywhere, not just coastal regions and faction capitals. Their devotion to the Gods mechanics have changed as well, with the Hound and Crow no longer providing the RoR "The Ice-Forged Legion" Hellcannon unit and the global plague. Instead they provide access to and Exalted Hero of Khorne and an Exalted Great Unclean One respectively.