This guy has wrongly predicted the d400 before, further even NikonRumors, which often gets inside tips and publishes rumours that are certainly suspect has indicated they have received no indication at all that the d400 is forthcoming and has looked on this tip as questionable. In short, a d400 may be coming, or may not be, but I wouldn't base my decision on one report that has already been wrong.
The refresh cycle for a d400 was actually 2011 prior to the flood, further I find the reasoning for releasing the d7100 when it was over a d400 questionable - nikon has the d3200 and d5200 for volume sales, the d7100 is not as much a volume seller. Also the d7100 had to be developed, whereas if this report is correct, the d400 was ready to go. Much cheaper to tweak it and release.
It is likely if this tip is accurate further tips/rumours will leak out over the next few months.
Of course D700 shooters waited 5 years for a replacement and got...a split in the FX line that the d700 used to occupy - a d600 and a d800 - neither of which are considered by many d700 users to be true replacements - so we adapt. There is a lot of 'the d400 will have to have these features' based on how the d300 related to the then FX line-up features. Now that Nikon has kind of turned the FX line-up on its head, I don't think we can be too confident in what a D400 would look like.