Does you need a camera better than the D3. Only each person themselves can decide, but it is pro level and can be got secondhand. The D4 may be better but really only time will tell once people use and can give feedback (I have no doubt though it will be a great piece of kit). I would doubt (and no disrespect meant to op) that when a question is asked about these 3 cameras that the person asking has the knowledge to make the most out of any of them. A d4/d3 comparison, fair enough but the d800 is only similar in that it is a full frame. The ISO and speeds of these cameras will be on opposite sides of the fence in performance so ultimately will appeal to pros with different needs