After the first two Age of Mythology expansions were Chinese and Japanese, with no more updates guaranteed beyond that, a lot of us were worried that that would be it. Its player count numbers on Steam don't look great, so we thought it might get put out to pasture like AoE3 did. But we're now being promised the Aztecs, as well as a new major god expansion for Demeter, and a major visual update which "introduces dynamic blood systems, prismatic essence for myth units, and evolving transitions that make each skirmish feel visceral and alive – exclusive to Expansion Pass owners".
That "Expansion Pass" is good news, too. AoE3 had one more expansion announced, but it was cancelled along with the cessation of future development. But this one is going to be taking people's money as early pre-orders. That gives them an obligation to follow-through to a much greater degree than something that was only announced.
AoE2 gets a new South American expansion with 3 new ranked civs: Mapuche, Muisca, and Tupi.
AoE4 gets two new expansions, one "will feature a sweeping story inspired by Chinese history" in a campaign, and the second will bring 2 new civs, one of which is Vikings. I kinda hope they don't call them that though, considering the trend so far has been that civs are largely named based on actual historical political entities. "Vikings" was historically a term for a thing some people did. The actual people were the Danes or Norsemen.