Fire Emblem Heroes has shared news of the next version update, which is scheduled for early January 2019. You can find the information via the in-game notifications, but for your convenience, we’ll go over them here.
Firstly, as teased in the latest FEH Channel, Heroes with beast weapons will finally be arriving. No new information was shared, so we still only know of Tibarn and Nailah. But existing skills have been updated to account for these new weapons.
Next, Legendary Effects and Mythic Effects will play a slightly bigger role. In Aether Raids, Legendary Heroes will receive Mythic Effects if a Mythic Hero is present and both of their elements are aligned with the current season.
Likewise, Mythic Heroes will receive Legendary Effects if a Legendary Hero is present and both of their elements are aligned with the current season. This applies for all battles outside of Aether Raids, except Blessed Gardens.
For example, the current season is Water, Wind, Light and Dark. So if you have Legendary Fjorm (Water) and Mythic Eir (Light) in the same team, Fjorm will get a stat and Lift boost in Aether Raids, while Eir will get a stat boost in Arena etc.