Overall, Isgreen didn't really go into the details but he said the game will build on the resource and progressing model from Age of Empires II. The game will have four resources that will be used by all civilizations, but it appears some civilizations will use resources differently than what we're used to.
Similarly, Age of Empires 4 will have four basic ages but not all civilizations will play by this four-age rule. Isgreen also mentioned that from a presentation point of view, the new Age of Empires will bring the ageing up aspect to a level no one has ever seen in an RTS game before.
That last point is interesting. Ageing up would always update your civilisation’s building set – couldn’t have Iron Age Romans living under Stone Age animal skins, obviously – but the idea that presentational changes will be wholly new to the genre is an exciting promise.