Talking about daemon releases, I wonder if we would see any new types of Daemons. As far as I can see, there have been very few new types of daemons released since the very start, 30+ years ago.
Realm of Chaos: Slaves to Darkness describes the servants of Khorne/Slaanesh:
The Bloodthirsters, Greater Daemons of Khorne.
The Bloodletters, Lesser Daemons of Khorne
The Fleshhounds, Creatures of Khorne
The Juggernauts, Steeds of Khorne
The Keepers of Secrets, Greater Daemons of Slaanesh
The Daemonettes, Lesser Daemons of Slaanesh
The Fiends, Creatures of Slaanesh
The Mounts of Slaanesh, Steeds of Slaanesh
Realm of Chaos: The Lost and the Damned describes the servants of Nurgle/Tzeentch:
The Great Unclean Ones, Greater Daemons of Nurgle
Plaguebearers, Lesser Daemons of Nurgle.
Nurglings, Daemonic Servants of Nurgle
Beasts, Creatures of Nurgle
The Lords of Change, Greater Daemons of Tzeentch
The Pink Horrors/Blue Horrors, Lesser Daemons of Tzeentch
Flamers, Creatures of Tzeentch
Discs, Steeds of Tzeentch
Outside of these, I can think of
Screamers of Tzeentch (unmounted discs?)
Brimstone Horrors of Tzeentch
Plague Toads (FW), creatures/steeds of Nurgle.
Rot Fly, steeds of Nurgle.
Furies - Unaligned
Daemon Brutes (FW) - Unaligned?