We were finally given a look at Age of Empires 4 today during X019.
Age of Empires 4 is still in development, which means a release date was not provided.
What we do know, is it's set during the medieval period and the factions shown in the trailer are the Mongols and English.
The game is still in its alpha stage, so we will have a bit of a wait.
Until then, you can always play Age of Empires 2: Definitive Edition which arrived today. It's also available through Xbox Game Pass.