The game cartridges for the 3DS can apparently hold up to 8GB, although they are unlikely to hold that much.

While the Nintendo DS cartridges can only hold up to 512MB it seems Nintendo have bigger plans for the 3DS. Macronix, a Taiwanese company that is responsible for producing the cartridges, are apparently producing the cartridges so that they have a 8GB capacity according to Kotaku.

However, while the cartridges can apparently hold up to 8GB rumours suggest that Nintendo may be implementing a 2GB limit on games. While this may be the case initially it is possible that over the span of the console's life more of the memory will be used.

Please remember that at present this is unconfirmed by Nintendo.