dj - the problem with what you describe is two-fold for those of us that shoot birds and small animals. Others have said more than I am about to say about not having a replacement for the D300, albeit in different posts.
1. The ergonomics, and features like autofocus tracking are much better to me on the D300 than the D7xxx cameras, and the viewfinder, body build and weather proofing as well. I have lost track of how many times I have accidentally hit buttons on the back of the D7000.
2. I use the aps-c format for more pixels in the center of the frame in conjunction with the 1.5 crop factor. A 24MP full frame is going to have less pixels than I want in the center of the frame. So unless Nikon can make all of those MPs work in either mode which is unlikely I feel like I am loosing reach and resolution so would have to buy an 800mm lens instead of using my 500mm with tel-converter which means carrying more weight. At 70 I really do not want to carry more weight, so will definitely not being doing that.
I think the D600 will be a great camera for most people shooting where they can change position quickly for framing their shots. I do not have that luxury when a bird is sitting on the other side of a body of water, or flying at angle that is going away from me.
You made valid comments, and you speculation is every bit as good as anyone else's. Nevertheless, there are a ton of photographers out there with similar needs so speculate that Nikon will not help themselves by ignoring this market segment. People like me will also buy a D800, or the D600, for the portrait and landscape quality, and happily use one of them for birding when we are close enough for a 1000mm or less lens to cut it. I am not buy anything (in fact have already sold a dozen FF lenses, just keeping the golden ones like the 85mm f1.4 ED ) until Nikon does something meaningful for their aps-c format because this is the format that works best for me. APS-C let's me cover from 16mm to 1500mm in 35mm format with the pixels where I want them for birding, inside that little aps-c frame.
Time will tell. I like the D7000, and it takes very good pictures, but I love my D300 more, unless I need a higher shutter speed which is THE great asset of the D7000, and actually the only reason I bought them. I have a D5100 too which is my goto camera for my grandchildren because of its tilting display which lets me get better shots without spending too much time on my knees. lol.
Nikon was too late, with not enough picture quality, on the V1 so after waiting to see what Nikon's response would be, if any, to Sony's NEX chose the NEX Series for its higher quality, and I love it. I have used Nikons since I was a kid so have a high regard for their people and company. Nevertheless, I think I am getting old faster these days so perhaps less willing to wait. There are whole bunch of baby boomers that will probably feel similarly right behind me.