Nintendo is planning a March release for a downloadable tool allowing transfer of save data from a cartridge-based 3DS game to a downloaded version of the same game. The news comes from a special mini Nintendo Direct released only on the Japanese eShop today.
In Japan, Nintendo will have 46 retail games on the eShop by the end of the month. Culdcept, Calciobit, Fire Emblem: Awakening, and Nintendogs + Cats will help the eShop reach that total when they go digital on January 30. That said, we're guessing this tool is primarily for people doubling up on Animal Crossing.