I don't see where there is room. A new D400 would have to be priced at $1,800 at launch, and would probably settle in at $1,599 after a year or so. By then, the D7100 will be selling for $1,000. FOr the extra $600, what would we get? Probably the same 24MP sensor as the D7100. Probably the same CAM3500 AF system with D4 algoriths. Probably the same FPS, maybe one more with a grip (though difficult due to limits of the high res sensor) - and FPS is really over-rated once you cross 6 FPS. The same dynamic range and high ISO performance.
So, what would we get for $600 more? A bigger, heavier body that really isn't any more durable (the D7100 is mostly magnesium, at least where you need it). Better weather sealing,...maybe? That is worth something to working pros who work in harsh conditions. The "pro" control layout. This is only an issue if you switch between a D4/D800/D700 and a DX body regularly. Otherwise, you can adapt. The D7100 provides 99% of the external control of the pro bodies, just in different locations (AF-On button excepted). I believe that there just aren't many photographers that fall into that category (though the percentage is certainly exaggerated on this forum).
So, is that worth $600 more? Maybe to a niche group of photographers. In this hyper-competitive market, I doubt Nikon can afford to cater to niches. In fact, nothing about their DSLR lines of the past three years suggests that they are interested in doing so. And, Canon's "pro" DX camera, the 7D, is getting as long in the tooth as the D300s. No sign that they are catering to that market, either.
So, I don't think there is room for a D400, now that the D7100 has stolen nearly all of it's thunder for half a grand less money. More likely, they'll tweak a D600 or D800 and create a true FX D700 replacement. And, I'm not so sure how likely that is, either.
Two comments specifically on the article: 1) I believe that 8-9 FPS is impossible on the 24MP sensor. The high res sensors seem limited in that way. Otherwise, how do you explain the relatively low FPS of the D600 and D800?
2) I think a D400 would have the same meter as the D7100. I believe that every other DX flagship has had the same meter as the lower model: D200/D70, D300/D90. And, really, how much better of a meter do you need? My nearly 10 year old D50 nails exposure dead-on nearly all the time. For that matter, my old N80 metered just fine. Canon's meters are generally considered to be inferior to Nikon's, and a million publishable photos are taken everyday with Canon cameras.