This list was sent in today showing which models are sold out, possibly giving some indicators of what might be getting reboxed soon, or even replaced.
via a reader on Faeit 212
There are a lot more models going the way of the Sold Out list. Some aren't even that old yet!
Grey Knights
Castellan Crowe
https://www.games-workshop.com/en-US/Grey-Knights-Castellan-Crowe
Space Wolves
Grey Knights
Castellan Crowe
https://www.games-workshop.com/en-US/Grey-Knights-Castellan-Crowe
Space Wolves
Space Wolves Wolf Guard
Space Wolves Transfer Sheet
Dark Angels
Dark Angels Transfer Sheet
https://www.games-workshop.com/en-US/Dark-Angels-Transfer-Sheet
Astra Militarum
Dark Angels Transfer Sheet
https://www.games-workshop.com/en-US/Dark-Angels-Transfer-Sheet
Astra Militarum
Cadian Heavy Weapons Team
https://www.games-workshop.com/en-US/Cadian-Heavy-Weapon-Team-2
Imperial Knights
Knight Errant
https://www.games-workshop.com/en-US/Cadian-Heavy-Weapon-Team-2
Imperial Knights
Knight Errant
Knight Paladin
https://www.games-workshop.com/en-US/Knight-Paladin
https://www.games-workshop.com/en-US/Knight-Paladin
Chaos Space Marine
Dark Eldar
Succubus
Tyranids
Tyranid Swarm
Carnifex
As you see, some lift a few eyebrows, like the Succubus and Carnifex!
