They never called the DS a gimmick..also, it wont since SONY has announced long ago that the Playstation 3 will offer 3d gaming/movies this year..
although the need for glasses is there. If a 3d tv costs that much, I can only imagine how much a 3DS will cost with a screen that can do 3D without glasses, if tv's with glasses cost well over 2k.
Gimmick is exactly what Sony called the DS.
""With the DS, it’s fair to say that Nintendo stepped out of the technical race and went for a feature differentiation with the touch screen,” Harrison continued. “But I fear that it won’t have a lasting impact beyond that of a gimmick – so the long-lasting appeal of the platform is at peril as a direct result of that.”"
3D is easy to do on a handheld, multi-layer LCD technology has been around for a while. It won't be that expensive to do.