I was at an EB games today and a Sales Rep from Nintendo was discussing the 3DS and other highlights from E3 to the store manager. I asked her if she knew what the release date was and she said that it would most likely be released in March/April 2011. I know its not an official word but I figured it was worth sharing.
They may be waiting to see what kind of business the new Sony and MS peripherals do, and then decide whether people will have cash remaining to burn on a new handheld. That said, the person you spoke with may simply have been parroting what Nintendo has already said: that it will launch worldwide by the end of their fiscal year (March 2011.)
Some rumors insist it will be released in October in Japan exclusively, which might still suggest a Holiday 2010 release for other regions, but then again perhaps not. We won't know until they give us more word. Maybe at Games Com or TGS.