Sensor-wise, the D400, if it is DX format, could very well be nearly identical to the D7000. There is a good chance that they will share the same sensor. Maybe not, but still something to think about. Think D90 sensor versus D300 sensor. Pretty much the same.
I would say that the D7000 looks like a worthy upgrade to the D200. All the key areas, like speed, metal body, AI lens compatability, etc are there. Just a few relatively minor things geared more toward the professional, like CF card, remote terminals, control layout, etc, are missing on the D7000.
Also, the D400, if and when it arrives next year, may be over $2000. Just something to think about.