No manufacturer can afford to release a new body that's plagued with issues... Looking back over the D80/D200/D7000, every camera had it's share of internet chatter on things like overexposure to dust and back-focus.
There HAVE to be some bodies that won't be perfect, but I doubt it ever gets to the level of broad statistical significance.
On the other hand, if YOU get a problematic body than it's a 100% hassle.
Most reputable retailers have a generous return policy, and Nikon is a great company. Chances are you're just going to get a wonderful image-making machine, at a terrific price.
Bear in mind, once you purchase any digital camera you're buying into a benchmark that WILL get surpassed...
I for one think a D400 is possible, at $1700 bucks.
The buffer means almost nothing to me, but sensor quality and ISO perfomance. The D7000, at $1100, blows the doors off my D200 that cost much more. So, perhaps a D400 will have some neat and unique aspects (like a fully integrated battery grip). I doubt it will be a quantum leap over the D7100, because the 7100 has a great deal already packed in.