I could be wrong, but I vaguely remember the announcement at FanFest saying we'd be getting "new deep dungeon type content" or something along those lines - the way they phrased it sounded like it could be something different.
This slide says "New Plans for Deep Dungeons", rather than simply "New Deep Dungeon". Makes it sound like they acknowledge that a change is needed.
I'm hesitant to trust announcements like this after how other features of Dawntrail turned out in practice, but maybe it's cause to be somewhat (cautiously) optimistic?