But we need a new Age of Empires IV to, they are great community mods that Microsoft can put attention and make it an official expansion to Age of Empires III.
Age of Empires IV can be based on the Great War were exist empires, so the game can still named “Age of Empires” and have a good consumer sensitivity for the work of others games like Battlefield 1, so can be a RTS version of this, i think is good idea make it now because later is to late 
Here a video of a mod of AoE3 based in the Great War
Anyway if make AoE4 is imposible please put attention to the community work and help to make it an official expansion the mod Wars of Liberty or make a Steam Work Shoop for mods likes this one People have sensitivity for México for all the media talking about the Trumps Wall so i think is a good comercial movement to.