UPDATED: The update is here for North America.
The European edition of the Nintendo Download went live today, and it has an interesting update for Letter Box, what is called Swapnote here in North America.
The April 4 update includes: the ability to “take photos and record sounds you want to attach to your letters from within the software. You can still add them from the SD Card.” You can also “attach photos and sounds when you reply to letters, […] Choose a different ink colour for each page, […] and “Filter letters by sender in the letter list.” They say, “To download the update, visit Nintendo eShop. All data will be [...]