As of today I don't have any details on the Nikon D400 DSLR camera (or whatever the D300s replacement will be called). The only information I received is that the Nikon D400 will be released in 2012 after the D800/D4 announcements (I was told in March). It's just too early to consider this information as reliable. Maybe Nikon will really try to get it out before the London Olympics. The Nikon D400 is supposed to be a "bigger D7000" with a monster burst rate and tweaked AF system from the D4.
In 2012 Nikon will be announcing the D4/D800 plus a D7000 replacement (probably in August). Adding the D400 on top of those three cameras will really make 2012 a "Nikon DSLR year".
I am also getting some tips that a new Nikkor AF-S 24mm f/1.8G DX (no VR) lens is currently being tested. With the success of the AF-S 35mm f/1.8G DX, I will not be surprised if Nikon releases another DX prime lens.
[NR] probability rating for everything in this post is low at that point, about 30%.