NY Times has the scoop:

Mr. Fils-Amie said that future DS device will be more tightly integrated with its Wii console. Complete games as well as game samplers will be able to be downloaded into the Wii using its broadband connection, and then transferred wirelessly to the DS… “To aggressively drive DS business we need to provide other forms of entertainment to excite the consumer,” said Mr. Fils-Amie.

I suspect another update will need to take place as well as the DS can only play temporary downloads in its current state.