I've had a couple of thoughts about this. Along with the engadget article, there has been a reported sighting at a photo shoot in a Seattle coffee shop of a thin, black KDX-like device.
So I think that the new device might be something targeted at the business marketplace (Amazon has been actively seeking a high level executive to push into this area). It might also be the rumored K3, or it might actually be an el cheapo K2-.
I actually agree with the general thrust of sensualpoet's post, if not necessarily the specifics. Whatever new products Amazon decides to announce will likely be accompanied by some rebranding/repricing of the existing models. They need to get a cheaper reader out into the marketplace while also bringing a higher function device to the table.