I do not see the logic:
DX: Entry: D3300 a bit better: D5300 quite a good machine: D7100 ... logically when you want to go better go FF.
FF: Entry: D610 a bit better D750 something special: Df Lots of resolution: D810 Workhorse: D4s
If you have issues with the D7100, you will probably need more ISO performance, at this moment you will have to go FF. (My hopes are on the Samsung NX1, but they are low) You will get better results with a D750 and a heavy crop then you will probably get with any professional DX model (Canon included).
I will wait to see the test results, but I do not think so. Yes the 7D MarkII will outsell the D750, but not because it is better, just because people have the L lenses that go with the Canon.
The issue with the D7100 for many is fps and buffer size. Nikon has no fast Dx model. With the current Nikon lineup, you have to go to a D4s ($6500!) To get good speed and buffer performance. If you also want Dx reach, you have to crop down a lot of file size. That is not logical and a massive hole in the Nikon line-up.
Canon is very smart to see what Nikon does not want us to.