I am at the point now that I really don't need a D400 anymore. A couple of years ago yes it would have been great. If you still shoot a lot of sports I am sure it will be the best yet in the $2000- $3000 dollar price range, assuming Nikon really brings it to market.
Should Nikon announce a D400 DX camera this year, I may think about selling the D7000 and D300. Really depends on what features Nikon chooses to include for the money. If they only give you 8 fps in super crop mode, or video with limitations like you aren't allowed to adjust the aperture in live view it won't be worth it for me.