We haven’t heard or seen anything since the GamesCom 2017 Reveal Trailer. Why are Microsoft / Relic being so quite? There are a lot of fans awaiting more information. Hopefully we get news of it this year. E3? PAX? GamesCom?
It’s all speculation at this point. My best guess, not an announcement, is more info at Gamescom 2019 about AoE IV. However more info may not come this year at all. It depends on the current development status of AoE IV and what Microsoft is comfortable announcing, if anything before the look and feel is mostly there.
and especially not before 2 and 3 DE of which for this would be more likely this year with maybe some info on AOE IV for later.
Actually age of empires II Definitive Edition is going to being developed by forgotten empires, while age of empires IV is being developed by relic entertainment, so the two are most likely being developed in tandem with each other.