from rpgamer.net:

Nintendo of Japan updated the Fire Emblem website today with a teaser trailer for a new series installment for DS titled Fire Emblem: Monshou no Nazo Hikari to Kate no Eiyuu. That is loosely translated to Mystery of the Emblem: Hero of Light and Shadow. Reports are stating that this title is a remake of the third game in the series, the Super Famicom release Fire Emblem: Monshou no Nazo, which itself included a remake of the original Fire Emblem.

Along with the new version of the first game, Monshou no Nazo also featured a brand new scenario that was a continuation of events from the initial game and includes the same characters. Considering that 2009's Fire Emblem: Shadow Dragon was a DS remake of the original, it is highly likely that the new game, Fire Emblem: Monshou no Nazo Hikari to Kate no Eiyuu, will be the continuation. The only thing official right now about the game is the trailer, found on Nintendo of Japan's Fire Emblem site.