Oh yeah, no earlier than 2021.
From “Gamestar Age of Empires 4 preview” interview
For Shannon Loftis, it was important that the technology was 100 percent up and running before gameplay concepts were finally approved. And Adam Isgreen talks about the “tech debt” you wanted to avoid - the dragging along of old bottlenecks in the engine that you have to program around. This is one reason why Age of Empires 4 has no release date yet - it’s not even known if it will be released in 2020. At the moment I’d rather guess 2021, but that’s just my gut feeling.
They have to take all the time they need