Dawn of the Dukes DLC will be free for everyone who pre-orders AoE4

https://store.steampowered.com/app/1466860/Age_of_Empires_IV/

Pre-order Age of Empires IV now and get the Age of Empires II: Definitive Edition “Dawn of the Dukes” expansion as a free bonus in August 2021*.

So basically Dawn of the Dukes coming in August 2021