Well, we all saw this one coming. Because of the new features of the DSi, there will be future games that are "enhanced" for the handheld. These "Nintendo DSi Enhanced" games will make use of the handheld's features not found on the DS, like the camera.
Explains Nintendo's Masato Kuwahara, "For example, you will use these features if you want to create textures from photographs taken with the DSi camera." These games can still be played on the DS, except that it won't be able to utilize the features that are hardware-exclusive for the DSi, obviously.