Japanese Homepage:
http://www.nintendo.co.jp/3ds/afej/index.html
Think this is the 13th title of the Fire Emblem series. So far a Japanese and European release have been confirmed.
The game will be released in japan on the 19/04/2012 and sometime this year in Europe (probably Australia as well)
So far we know that the game wil have two heroes, this is one of them
and the second one is your Unit.
The game will also feature DLC. These DLC, if i understand correctly, are distributed as set, containing new episodes and maps. So you don't just by one map, but a new story.
In japan the first DLC will be available on the same date as the game and available for free until the end of May 2012.
You can find a new cel-shaded trailer on:
http://www.nintendo.co.jp/3ds/afej/movie/index.html
More on Fire Emblem:
Intelligent Systems' Fire Emblem World homepage (make sure to check out the sound museum)
Limited Edition 3DS Box & console
JPN box & eshop card (1000 Yen)