take a look at this.
you can see slightly after it's second holiday DS sales shot up to the 300 to 500K weekly sales in the summer and stayed there for about 4 years. if you align DS and 3DS sales the bump in DS sales will line up with 3DS sales around this march i think. with 3DS doing worse this holiday than last it won't be hard to imagine 3DS loosing a good 100 to 300K sales (Gen over Gen) a week in the summer.