This is not how Nikon typically does it. Typically, Nikon releases it's high-end body first, gets as many people to swallow hard and upgrade, then releases a less expensive body that does 90% of what the top body does. This entices the people who held out before, because they usually buy on a price point, to upgrade.
A classic example is the D800/D600. A lot of D800 buyers would probably have been satisfied with a D600, but it was too late. If I recall, something similar happened with the D3 and the D700.
This reinforces my belief that a D400 is not coming. If a D400 is coming, why not introduce that body first? Get a lot of us who are not quite satisfied with the D7000 AF system to upgrade to the expensive "Flagship" DX body. Then,...hit us with the D7100 that most of us would have been just as happy with for $600 less. But, Nikon didn't do this - probably because the D7100 IS the new DX flagship body.