At a GDC 2009 panel entitled, "Inspiration Behind Nintendo DSi Development," Nintendo's Matato Kuwahara let it be known that Nintendo is currently working on DSi-specific game cartridges.
Initially, it was revealed that DSi-exclusive software would be made available via download. Now it seems such software will also be sold through retail outlets.
Future titles will be produced on one of three carts depending on their audience: standard DS carts; DSi enhanced carts; or DSi-exclusive carts.
DSi enhanced carts will play on all versions of the DS and will include special, DSi-only features that are made available when played in the new handheld. If developers want to market their software specifically to DSi owners, then a DSi-exclusive cart will be used.
The two new cartridge types are still under development at Nintendo.
GDC 2009: New DSi Game Carts Under Development