Whether it be the DS Lite or the DSi, Nintendo has announced a spate of Nintendo DS hardware spin-offs in the last few years. The Nintendo 3DS is not a spin-off. It's worth pointing out, you know.
Nintendo released its Play And Watch series of handhelds in the early 1980s. Following that, the company released the Game Boy in 1989 and then the Game Boy colour in 1998. The Game Boy Color's successor was the Game Boy Advance in 2001, and it was spun off into the laptop style Game Boy SP and the smaller Game Boy Micro.
Following that line, Nintendo released the Nintendo DS in 2004 and followed that with the Nintendo DS Lite, the Nintendo DSi and the Nintendo DSi XL.
The Nintendo 3DS is backward compatible with the Nintendo DS line, Nintendo has announced. This means that the Nintendo 3DS is expected to have at least two digital cameras like the Nintendo DSi. It is not yet known whether they will be of a higher than the DSi's current 0.3-megapixel cameras. The official Nintendo announcement simply suggests this.