Hi Neil, You sound very disappointed and frustrated in these posts. It sounds to me like you want a new camera but you do not really need one as the D300/700 combo fits you and your needs quite well. Right now the D600/7000 would tend to be the 2 cameras that appear to mesh in the same way as your combo. Unfortunately they have short comings that you do not want to compromise so you are left out.
I was in a similar situation when the D300 came out as well as during the D80 and D90 upgrades to the D70. The D300 was more than I wanted to spend and had some features that I did not really need and the D80 and D90 left out features (or did not improve them enough) that I liked in my D70 so there was no new camera that fit my needs. I wanted one just for the better high ISO's and better overall image quality. I could not justify buying a new camera because the image quality alone was not enough to make me compromise, whether right or wrong. I had to skip a generation or 2 for Nikon to make a camera that fit my needs, the D7000 did the trick. You just might be in a similar boat. You are just far enough outside of the sweet spots for these new cameras that they just do not justify the expense or compromise.
Don't worry, you have managed to create some beautiful images with the cameras you have and I am sure that you can continue to do so. Nikon may have just done you a favor and saved you 3k, for now.
Marc There are always two people in every picture: the photographer and the viewer.-Ansel Adams