There are memory card readers for the DS that let you play MP3s and even movies and they are pretty good efforts. But they are not nintenfo supported and are aimed at the Homebrew audience, which essentially means that the average member of the public misses out on these sorts of things.
One example for me on the Wii is the photo channel. This could be expanded into a Music Channel and a Video channel, where you can play your MP3 collection off a USB HDD or video, or even utilise the SD card and the opera browser to be able to download this content for later play/upload to an MP3 player. This is the sort of thing Nintendo should keep rolling out in order to keep the console moving and it's sales momemtum positive. But as i said before where is the incentive if financially they are already raking it in?
Essay Pro