Looks like we can both claim to be right on this one!
The thing has been ‘launched’ and it appears that there are two classes of product. One which, like you thought, adds a clip-on lens in front of Apple’s camera (it doesn’t replace the sensor either). I agree this is pointless (and it is also rather expensive). The other, like I thought, does completely replace Apple’s camera, and so has its own glass, but it won’t be available until February and details are still sketchy, which is a shame because this is by far the more interesting product.