The Age of Empires fan preview event was all about Age of Empires IV, but the developers at Relic Entertainment also had some news on the Definitive Editions of the previous games. Both Age of Empires II: Definitive Edition and Age of Empires III: Definitive Edition will receive new expansions. As a conclusion to the Q&A session during the event, the question whether an Age of Mythology Definitive Edition is currently in the works was also briefly touched upon.
Without literally confirming its development, the team at Relic stated "nobody has forgotten about Age of Mythology." Responding to the fact that it's such an obvious game missing from the Definitive Editions, they said: "absolutely we know, we're not pretending that we don't know it's there." Concluding with a remark to "stay tuned", it's highly probable at this point that Age of Mythology Definitive Edition is currently in development.