In March 2009 - According to IGN Article
IGN said:There was a bit of news on the touch screen front during 2008, the biggest and most obvious being the announcement of the DSi, the second rehash of the DS. In addition to it being sleeker and brighter, it also includes a camera and an SD card slot. The system has already launched in Japan, and Nintendo of America has slated it for a March 2009 release.
IGN Article
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Thanks to War for reporting