The 2DS is unnecessary for these reasons
1) Nintendo can easily update the system software of the 3DS to allow you to turn the 3D on or off completely, and if they are worried about kids, have the 3D off by default, and if you want 3D you can turn it on with the click of a button.
2) it is not exactly portable in the sense we are accustomed to today. It does not exactly look like it'll fit in your pocket..maybe that is the intention so that you have to shell out more money for a carrying case to protect your system, as opposed to a clamshell design which protects itself relatively well. (next year, 2DS XL, it looks like an Ipad with two screens). And with the design, you have to worry about kids breaking the screens more than a hinge on a proper 3DS, which is a more expensive prospect to the consumer.