In an interview with Nintendo Now, General Manager Entertainment, Analysis & Development Division Takashi Tezuka and Manager/Producer Entertainment, Analysis & Development Division Katsuya Eguchi confirmed that not only is Animal Crossing in development for the Revolution, but also alluded to some form of compatibility with the Nintendo DS.
NNow: Are you in early development of Animal Crossing for the Nintendo Revolution?
T. Tezuka: Yes.
K. Eguchi: We are trying to make it compatible with the DS version as well.
Source: Nintendo Now