The trailer showed a convincingly cel-shaded game with a look similar to Dragon Quest VIII, with characters identified only by classes, including ogres, elves, and dwarves. A party consisting of multiple classes is shown running on a world map, and many of the series' familiar monsters, including various Slimes, are shown.
While Level-5 was responsible for the development of Dragon Quests VIII and IX, only Square Enix was named this time. We'll have more details following the conclusion of the event.
Update: A version is also being developed for Wii U. This release will have improved graphics, and will be playable cross-platform with the Wii release. In addition to this, the team is considering 3DS compatibility in the form of character transfers. Save your character to your 3DS to trade with others, basically.