They did. If you have the Nintendo Channel, check out the game page for City Folk. look at the specs of the game (you know like # of players...) and somewhere there it says Downloadable Content. Also Japan has already got some downloadable content which was a red pikmin hat. If you know someone who was the Japanese version of Animal Crossing City Folk and is connected to the internet, he should have it. And if you were to visit his town, it would load it into your game.
Also there is hacked downloadable content out there, but I would suggest not doing that.