A lengthy update on the Age of Empires Blog outlines extensive plans to continue to support Age of Empires II: HD Edition, including plans for the next patch as well as improved steam workshop support for the real-time strategy remake (thanks Polygon). They also announce they will be teaming up with the mod team behind the unofficial expansions for the game for a new official add-on. Here's word:

I am extremely excited to reveal that we’ll be working with the Forgotten Empires team to formally bring a new expansion to the Age of Empires franchise later this year.

We’ll be detailing the expansion throughout the year in developer blogs directly from the team, including one soon revealing the first new civilization. I’ll leave you with a teaser the team sent from one of the new units being worked on:

As with The Forgotten expansion, you can anticipate a lot packed in there, including new civilizations, campaigns, game modes, units, and more. If your focus is more on the original Age of Empires II experience, the new content development means you can look forward to additional support and features that benefit every owner. Since launch, AoE II: HD has come a long way, and with the help of the FE team and Skybox, this year is going to be the best yet.