Why would you even want to be shooting an APS-C camera these days when the majority of photographers have moved on to FF? Dramatically better low-light ability and better DOF control are two no-brainer reasons to use FF over APS-C.
Should one choose a camera by picking one they need, or picking one everyone else is using that doesn't have what they need? All the new FF cameras have slow burst rates and of course heavier + more expensive glass- exactly what DezM DOESN'T want.
If you shoot Nikon, you know that the glass for DX and FX is not dramatically different in size or price. Primes like the 28 f/1.8G, 50 f/1.8G or 85 f/1.8G are not heavy or expensive. DX UWA zooms are like the 12-24 f/4 are as expensive and as large as FF UWA zooms like the 18-35 3.5-5.6. Same for the 17-55 f2.8 and 24-70 f/2.8.
As far as weight, if the OP were concerned about weight, he'd likely look at one of the APS-C mirrorless cameras like the Fujifilm X cameras. But I'm guessing he prefers DSLR ergonomics and F-mount. But the differences in size and weight between FX and DX are minimal, and since many DX use FF lenses like the 70-200 f/2.8 VR and since many DX consumer and prosumer zooms can be as expensive as FX zooms, there are no dramatic difference in prices.
Stop projecting YOUR wants onto him.
I'm not projecting anything on anyone, surely you are joking?
If you look at the OPs website there are very few, if any, images that he couldn't have made with 6 fps vs 8 fps. In fact there are very few sports/action/wildlife images at all, AFAIK. There are tons of wedding / event type images, engagement portraits and some nighttime cityscapes, all of which would benefit far more from the superior IQ of a FF DSLR than another APS-C DSLR.
As for the D400, it's true there is a hole in Nikon's lineup, but I am guessing there aren't enough DezM's to support such an endeavor.
Only time will tell, but based on the OPs website, to get all worked up over an extra 2 fps vs the D7100 or buffer size is ludicrous. The D7100 is a class leading DX camera, and there is pretty much NOTHING you cannot do with a D7100 that you can with a D300s or K3.
If I were the OP, I'd either buy a D7100 and work around any perceived inadequacies he felt it had vs the D300s, or I'd stop messing around with APS-C DSLRs and buy a D610, a camera that will make the biggest improvement for the types of images he makes out of any of these cameras.
If a D400 is announced, it will easy to sell a lightly used D7100 or D610 on Ebay and purchase a D400, if he still felt he needed such a camera. I'm guessing that after he shoots with either camera, but in particular the D610, he won't want to let it out of his hands.
.....if you felt that way about a D610, and want to stay DX, why NOT a D7100? They're darn near identical (yes, slightly larger and a bigger sensor).