That's a very interesting article.
I agree it's somewhat unlikely that they would actually put a dSLR on the market. That's not a product that would fit in their philosophy of design. Or let me put this another way: that's not what Jobs would have wanted.
I don't see them implementing optical zoom into iPhones, at least not until that technology gets a lot more compact. The option of getting a Nokia Pureview kind of system seems more viable.
The scenario that seems most likely to me is that they invest a lot of R&D into sensor-design and camera unit performance and try to expand the quality of iPhonography.
It would be very cool if designers were be able to come up with a replacable battery ring around lenses to give your body extra power for an extra couple of hundred shots. With this kind of technology that should really be possible.
Great article and interesting pictures.