Hidden Path Entertainment announced Age of Mythology Extended Edition for Steam over the weekend.
During a Twitch developer live stream of Age of Empires II: HD, released by Hidden Path last year, the studio announced the Extended Edition at the 43:02 mark but offered no additional details.
The fact that HD does not appear in the title suggest that the Extended Edition may be more than the usual graphical overhaul and will almost certainly include the Titans Expansion.
Hidden Path are also working on The Forgotten DLC for Age of Empires II: HD which is set for release soon. Age of Mythology was originally released by the now-defunct Ensemble Studios in 2002.