First things first, Minecraft: Dungeons is a brand-new game and not tacked-on DLC or a mod.
Dungeons will feature new mobs, including the corrupted Arch-Illager and its minions, who have enslaved Minecraft's villagers. When I asked Mojang about the possibility of hitting other platforms, they said Minecraft has always been a game "for everyone" but had nothing further to announce.
Minecraft: Dungeons is aiming for a 2019 launch, and Mojang describes the game as a "passion project" from a "small and dedicated team in Stockholm, Sweden". Not much more than that has been revealed, but here's the official site. According to the description, it will be an action-adventure game, modeled after classic dungeon crawlers.
The update will notably introduce new people into the game.
Minecraft: Dungeons represents the latest step from Mojang to branch Minecraft off into a new genre, with the most recent example being Minecraft: Story Mode.
During this weekend's MineCon 2018, Mojang twitterpated its worldwide community with some pretty awesome news including Minecraft: Dungeons. You will be able to play the game by yourself or with a group of up to four friends. Nefarious pillagers and beasts will also be unleashed upon the villages around each world. "Fight or flee through canyons, swamps and - of course - mines!" Hammers, swords, magic, and other weapon combinations were spotted in the trailer to show some of the options players will have. Although details about the game weren't announced, it is slated to arrive sometime in 2019. It'll be interesting to see if more will come down the line considering the popularity of the franchise.