It looks like you won't have to swap cartridges any more.
In a move that mimics the Xbox 360's ability to install games to its hard drive, Nikkei is reporting that Nintendo's 3DS system will allow users to copy cartridge-based games to internal memory.
Once a game is "dumped" to the system's memory, it can be launched by selecting it from a menu listing the games stored on the system. Users will no longer have to carry their cartridges with them on the road in order to play multiple games.
Nintendo has yet to discuss this feature, so we'll have to wait and see if there are any caveats.