NR has posted a rumor they give 70% probability to, that the widely expected August announcement will be for a D4 and D400 (mirroring the D3/D300 announcement from 2007, when both cameras were launched sharing the new CAM3500 autofocus system).
Also in the posted rumor, NR claims his source says 2012 for the D700 replacement.
Our take: D4 and D400 in August wouldn't surprise anyone - in fact if they don't come in August it will be more of a surprise. As for the D700 replacement (D800?), that could be next week, or could be a year away. The D700 came out a few months after the D3, sharing the same sensor, so that lends itself towards speculation that the D800 will have the D4 sensor, and come out a few months later (probably 6-9 months). However the D700 is widely believed to have cannibalized D3 sales, hence no D700s with the D3s sensor. If this is true, we can expect the D800 to be something other than a mini-D3.
Source: NR on 6/27/2011.