The official website updated with info and a trailer aboiut a new Fire Emblem game for the DS: Fire Emblem: Monshou no Nazo Hikari to Kage no Eiyuu (Mystery of the Emblem: Hero of Light and Shadow).
Like Fire Emblem: Shadow Dragon, released in 2008/2009, the game appears to be a remake of another NES game, Fire Emblem: Mystery of the Emblem which is the 3rd game in the series, itself a remake of the first game, known in the game as book 1, which also included a new story line, book 2, which is likely what the new remake follows.
You can check out the trailer over at the official Fire Emblem website.