The game, for the Wii U, is called Illusory Revelations #FE. It's set in modern-day Tokyo. Holy shit.
It will be out in Japan this Christmas. The game was actually announced briefly around two years ago, but then went quiet. This trailer is not quiet.
If you're wondering why some of the comments below are so... excited, it's because this is a dream pairing. Shin Megami Tensei is one of the best RPG series around, and Fire Emblem is just the best, period. Putting them together is the kind of thing you joke about on April 1, not lose your mind over on April 2.