Just to be very clear since my hints at this are not getting through...
I would consider the D400 a consolation prize. The D400 is not what I want, but it is a complicated lesser evil I might accept. I don't believe there will ever be a D400 and, if Nikon had done the line right (just doing what they have been doing for the last 5 years) I don't see a legitimate and *compelling* reason for one.
I do respect the reasons why a lot of people want a D400, but their reasoning mostly has to do with being buried in DX glass, which I am not. I have the D700 so I have gotten more or less past that (except the ultra-wide problem, where all I have is the 12-24DX).
The D800 could have been a good solution to the D400 problem, albeit at quite a price. But, from a sports/wildlife perspective it suffers from two fatal flaws...
1. It does not shoot 8fps *in DX mode* and I can't see any engineering reason why not. It is not a bandwidth issue; the D600 pumps more megapixels per second to the buffer. It is almost certainly not a shutter speed/cost issue; The D700 proves that.
2. It should have a Func button (Fn now) option to quickly switch between DX (or 1.2, et al) and FX mode.
If it had both those features it would 99% replace the need for a D400. That Func button option is really important to me and I can explain why if anyone can't figure it out. This is a real mystery to me because it is truly cost-less, aside from some firmware programming.
(the 1% is the viewfinder problem but that would not be a deal breaker for me)
I think 15mpx DX, with a full stop or so better high ISO performance than the D300 would be great. It would make the D800 perform more or less like the D700 in terms of noise, but with even greater sensor density.
While the D800 is more than I want to spend, it would literally be like having two cameras in one. I don't need two front line cameras; I need FX and at least 12mpx DX sensor density. I spent more on the D700 and D300 and I bought the D700 quite reluctantly.
The thing that motivated me to buy a D700, that put me over the top and made me spend more than I ever had or wanted to spend on a body, was the 8fps and the thinner DOF. I shoot jousting every fall, I am very serious about it, I've shot it for 8 years now, and I need 8fps, or more. The thinner DOF solved a very problematic crowd isolation problem that I had. It is perfect for that sport and it took me over the top.
The D800, with my mods, would not solve that problem. I would have to keep the D700 just for jousting. Six fps just doesn't cut it, neither would dropping back to DX DOF. I don't pay serious money to go backwards.
But the D800 would be a good compromise and solve some wildlife problems. The 36mpx is probably more than I need (or maybe want in most cases) but it is one way to get to 15mpx DX.
But Nikon decided to "cripple" the D800 in those ways, especially the DX frame rate. Given that there is no apparent interest in a D400 it appears to me that Nikon just doesn't want anyone shooting 8fps anymore. Unless they pay $5K for the privilege, and even if they pay up they can't shoot DX sensor density at 8fps. The D4 doesn't even cut it.
If there were an imminent D400 then I could understand the crippling, maybe. But since there will likely be no D400 forthcoming, I find Nikon's decision there incomprehensible and the D800 issues are a key part of my own problem here.
I'm actually in no burn to replace the D300/D700, under any circumstances. I've spent enough the last 8 years. I'd like to wear a couple of cameras out, for once. But when I look out on the horizon at that day when I wear my cameras out (with 80K+ frames each) I see no future that excites me.
The old Nikon would have made the D800 and/or the D600 irresistible for me. The new Nikon... very different story.
I too agree the D600 should have been called the D6000. It is a D7000 feature set with a bigger sensor. That's it, as far as I can tell.
When I first saw the specs on the D7000 I was both amazed and horrified. Amazed because the push of Pro features to the D300 was continued to the D7000 (albeit missing very critical deal breaker features for me).
And horrified because I had trouble visualizing a D400 next to it. And other people felt the same. Many started to question if the D300 was an evolutionary dead end. I think they were right and that was my fear at the time, which unfortunately seems to be playing out. Not just for the D300 but for the D700 (that part I did NOT foresee at that time).
The winners here are the old D80/D90 users. The D90 user gets a great upgrade, with the same basic ergonomics and better feature set, for about the same money now. The D7000 and D600 to them is what the D200/D300/D700 was to "us". To the third decimal place.
Me, I have to pay triple and even then I can't get what I want - and have right now.