Roshan -- I have been watching this thoughtful thread that you initiated, and in looking back, Nikon has not always created direct lineal descendants of each camera. For example, the D200 was a direct follow-on to the D100. But the D300 was an obvious quantum leap and the D700 was simply a "WOW" addition, seemingly out of nowhere after the FX sensor made its first appearance in a Nikon in the D3. In essence, I see no real predictable "plan." Instead, Nikon seems to be conducting constant engineering to apply new technologies and innovations, and gathering them up and introducing them periodically, often I think, in response to competition. Sometimes we see incredible leaps and other times we see incremental improvements. But for sure, we see new choices.
But what fun would we have speculating on the "next" Nikon if they were completely predictable?