The NOA Twitter feed announced a couple of hours ago the release window for AC:3DS. While it's not a firm date, it at least gives us some inkling of when (or even if, for those of you still in doubt) it would come to US.
<blockquote class="twitter-tweet"><p>Animal Crossing is launching for Nintendo <a href="https://twitter.com/search/?q=%233DS"><s>#</s><b>3DS</b></a> during the first half of 2013! Tell us your favorite Animal Crossing memory.</p>— Nintendo of America (@NintendoAmerica) <a href="https://twitter.com/NintendoAmerica/status/240919851361783808" data-datetime="2012-08-29T21:12:23+00:00">August 29, 2012</a></blockquote>
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Animal Crossing: The other oxygen.