Apparently, Nintendo has previously stated that all downloadable games will be stored on flash memory cards.
Strange.

We came across this patent today, filed in February 2004 and renewed only recently. Here, have a read:

"An existing video game system is modified to include additional communication and storage capability via a modem and hard disk drive. In accordance with one embodiment of the present invention, the primary system security features are incorporated into a video game system expansion device having a hard disk drive.

"The security system does not rely on the relatively insecure video game system. The present exemplary embodiment focuses security control in a disk drive/mass media controlling engine which is physically disposed within the expansion device housing as close as possible to the hard disk drive and the downloaded video games and other data it is designed to protect. Security features are incorporated into, for example, a disk drive controlling processing engine to provide security features which extend far beyond simplistic password systems which have heretofore been utilized in conjunction with disk drive controllers.
"In accordance with an exemplary embodiment of the present invention, the disk controller also incorporates an encrypting engine which encrypts in accordance with a highly secure encrypting algorithm. A further level of security is provided in the illustrative embodiments by partitioning the hard drive into various partitions whose security/accessibility is tightly controlled. Each application program, e.g., a video game, has a predetermined number of private partitions, including a read only encrypted partition."

Bit long winded isn't it? Here's how we translated it:

A console will include a hard disk and communication capability (internet). It'll have a security system and the ability to download stuff onto it.

Sounds like it could be the Revolution. But might apply to the GBA or DS 2. We tried to get hold of Nintendo, but alas could not get comment at time of going to press.