Lets face it folks, Nikon is still a business and the only objectives they absolutely have to meet are profitability and return for their investors. The Pro level equipment is most likely not a money maker for them. I would estimate that over 80% of their R&D dollars go into developing technology for this tier. While this technology that eventually trickles down to the pro-sumer and enthusiast level equipment it is usually once the a newer version emerges. What Pro level products do achieve is an incredible amount of media attention and excellent brand development and recognition.
My guess is that Nikon wants to sell cameras in this order:
A D3 will no doubt sell for up to 20X the amount of a typical Coolpix camera and net a profit more than an handful of Coolpix are worth. But I would bet that Nikon sell 100+X Coolpix for every D3. A similar argument can be made for the D40 to D300.
Back to the FX/DX argument, DX will be around for some time yet. For a purely business perspective the DX cameras are worth a heck of a lot more to Nikon's bottom line.
Well that's how I see it anyway.