I agree, we do need a D300s replacement, I have a D7000 at present. I shoot wildlife and landscape and in the absence of a D400 to replace my D7000 I took the plunge with a D800 after months of pontification. I took a risk and sold my beloved D700 so therefore replaced my Landscape camera and in hope that the D800 would satisfy my wildlife needs.
So far for my landscape needs it replaces my D700 admirably, for wildlife and apart from the low fps and lack of x1.5 crop factor, likewise it is proving to be a very capable camera. Whether it will do as well as a D400 for wildlife only time will tell, but the future looks promising.
I look forward to a D400 (if a new DX semi pro body ever materialises), but in the meantime I have no grumbles with the 36MP sensor and downsizing the image after cropping back to the APS-C sensor equivalent.