There are many parts of history in the game you haven’t covered such as the celts, Thracian / Dacian campaign, the Parthian - eastern resistance, Nubian/numidian campaign, Xiongnu / Scythian Campaign and many more interesting parts of history that don’t fit any other game in the franchise.
If you can’t add more content why not at least add the rest of the campaigns to 2 de
While it would be great to see. Realistically I doubt it would happen.
There are a lot of things they could have done but all in all DE is more or less just a modern version of the unofficial HD mod patch which was updated to have most of the same changes.
Best way to revive the game would be to add an exclusive DLC expansion that adds 4 civs 2 new unit lines and maybe add an additional line to an existing unit. This is similar to what Rise of Rome did.
The focus of the DLC could be real easy. As there are several more Bronze Age civs and there is the obvious follow-up to the Rise of Rome with the Fall of Rome.
Alternatively make Classical mode available online with it’s own ranked ladder and an option to play with the original balance. Which is ironically still the competitive standard for the Asian scene.
I also doubt any major additional updates to Return of Rome as well. Given how it only attracted casual attention and the entire purpose of it was to try and bring in the Asian scene from AoE1 but completely failed at doing that.
As such nobody plays seriously. AoE2 fans prefer their gameplay and AoE1 fans prefer their gameplay. So Return of Rome was always doomed to fail.