The German magazine Fotomagazin has a special Photokina report that includes also a new front view image of the Nikon D600. The picture is probably photoshopped, but it's a very close representation of how the real D600 will look. You can see the entire article here (in German) - the text is just a repetition of what I have been reporting in the past few months.
The upcoming Nikon D600 DSLR camera will probably be a mix of D800 and D7000:
The D600 seems to have a dedicated video recording button and headphones jack like the D800.
Here is a Nikon D800 and D600 size comparison sent by a reader - it's not the best in terms of proportions due to the angle of the leaked D600 images: