The category of a camera is not affected by the user. The quality of pictures that come out of the camera is affected by the user, but the camera itself is not. A professional camera always remain a professional camera, regardless of time period or the user. A D2 series camera, like a D3 series camera, will always be a professional camera.
All this talk of the user affecting the camera, such that a "noob" user of a D3s makes it an entry level camera, and a "pro" user of a D3000 makes it a professional level camera is bull. A D3s is a professional camera, and will always remain that way. A D3000 is an entry level camera and will always remain that way. If a D3000 in the hands of a pro makes it a pro camera, there would not be any working pros using a D3.
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An entry level camera provides some measure of controls over basic essential settings, an intermediate range camera provides more controls and more features, a pro camera offers excellent build quality, controls and non-gimmicky feature set (i.e. no Auto mode, creative filters etc). This is what separates them. The user affects the photos that come out of the camera, but the user does not change the camera. Image quality is not what separates the pro bodies from the entry levels (otherwise nobody would buy the D300s over the D5000), but rather, better accessibility to controls, better camera grip, battery life, build quality etc.
