The Nikon D800 book triggered a series of new tips and leads. Those are the most reliable rumors I received so far (please note that because a potential announcement is months away, some of the specs and/or release dates may change):
If true, this line up will indicate that Nikon will move away from the D3/mini D3 (D700) DSLR lines and create two more distinguished camera products. The D700 probably did cannibalize some of the D3 sales which (I guess) triggered that decision (otherwise they could continue to use the D3s/4 sensor in a D700 body).
No word on a D300s replacement yet.