Thom's predictions for 2013...

The D7100 would be higher sales volume overall (less expensive cameras within the same line are nearly always higher volume), but the D400 would probably be a higher profit margin and the D7100 will just continue on for the fairly good selling D7000, but the D400 might add a pretty big bump over the existing D300s sales.  All of this makes it's not so trivial to guess which might impact profits more.

Nikon's FX strategy of introducing the more expensive camera first tends to maximize their profit (ignoring the effects of having to respond to the timing of specific competitor's cameras).  If Nikon introduces the D400 6 months before the D7100, they will attract more volume to it than if they introduce it after the D7100 because some people will be tempted by the D400 that might have been satisfied with a D7100 and with no announced D7100, some of them would choose the D400.  So, if Nikon wanted to maximize the volume from their higher margin camera, they'd introduce the D400 before the D7100 much like they introduced the D800 before the D600.

Plus, the D7000 is still considered a fairly modern camera (it's not that old in the marketplace) whereas the D300s is pretty ancient.  The D7100 would probably get a bump to 24MP and a small bump in some other features, but it probably wouldn't change the needle as much on sales as a D400 that was really optimized for action and Nikon's only other camera besides the D4 that's really optimized for action shooting.  I personally think there's a fair

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John
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