I will go out on a limb and speculate that the D7200 will cost about $1,200 to $1,300, have a 24mp sensor, use native ISO from 100 to 6,400, have basically the same build quality and features as the D7000 with the exception of better video. The chief advantage of the D7200 over the D7000 will be better image quality, including cleaner images at high ISO, and better video.
I will speculate that the D400 will cost about $1,700 to $1,800 and will have a 24mp sensor, native ISO from 100 to 12,800, and basically the same build quality and features at the D300s with the exception of better video. Battery grip will not be built in as the D4 but will be an accessory as in the D300s.
The advantage a D400 will offer over a D7200 will be one stop better ISO performance, faster fps and larger buffer, more rugged build, longer shutter life, and the pro-type controls for direct access to ISO, Image Quality, white balance and bracketing found on what used to be the film rewind crank.
One caveat: It would be great if Nikon made a 16mp DX size sensor equal to the 16mp D4 FX size sensor and put that in the D400 so a D400 would have the same clean high ISOs that a D4 has just in DX size. In other words, put the electronic "guts" of a D4 into a D400 just in DX sensor size. That way when dealing with final print sizes up to about 24 by 36 inches a person could see no difference between an image taken with a D4 and one taken with a D400 at any ISO setting. Now that would be a real "bang for the buck" but it may cut into D4 sales too much.
As things stand now and most likely as they will be after the new D7200 and D400 are released the best "bang for the buck" will remain the D7000 line of cameras. Unless you really are going to shoot more than 50,000 exposures a year a D7000 line body will last until a D7200 is out and a D7200 body will last until a D7300 is out, etc.