If Nikon did not want to make a pro DX replacement for the d300, they probably would have told us so, because then, those of us waiting for such a tool, would switch over to FX without hesitation, well if we had no choice we would. Nikon would then selll us all FXs and further boost sales.
I think that they are introducing all of the "odd ball" cameras first, you know, the ones that have great appeal because of their super specs. but really are not for the D300 (or 700) pro/semi pro. users awaiting a replacement.
I might even consider buying a D800, D600 or even a D4 right now, they all seem so brill! oops.. better stop before I get to carried away and go out and buy one!
They want to see how many of these cameras they can sell and then they will introduce the legends of tomorrow eg, the D4s, the D300 replacement and the d700 replacement.
Yes, Even the D4 will have afew angry users when a D4s is introduced for afew dollars more.
My humble prediction.
D300 replacement 18 m.pixel, and low noise levels in settings over base ISO. with all the controls in the same place as on the d300/700 where we are used to.
D700 replacement 16 m.pixel, with all controls as above.
D4s 24 m.pixel D4 (and 300 dollars more than a D4)