Sweedish GAME retailers are already taking preorders for the Nintendo 3DS. The ad lists the 3DS as a Winter 2010 release. The Sweedish branch also released an E-mail ad with the exact same details.
This could simply be speculation on GAME’s part though. Or, they could know something we don’t know.
As of right, the only officially confirmed release details for the Nintendo 3DS is that it will be launching some time before March 2011. We will most likely find out a more specific release window at E3.
You can check out both ads after the jump. One of them has assests from like every Mario game released in the last 5 years.