The whole mythical D600 rumor is fascinating, because the Sony Alpha SLT-A99 coming in August is likely a full-frame 24MP camera. Even if Nikon uses the same/similar sensor with their typical Nikon "specs" there is often a lag of months before the Nikon "competing" model is introduced. So are we looking at December for a D600, or later?
On the other hand, the Sony DSLR-A850 didn't compete successfully with the D3x for a lot more money, even when both had 24.5MP sensors, plus, any D600 would be priced right in the same neighborhood as the SLT-A99. And one will be a dSLR, while the other will be an SLT, so will they really compete? It gets curiouser and curiouser.