No, they could not. DBC is interpreted. DBP is compiled. They also use different versions of DirectX and correspondingly, different feature sets and file formats (with some backwards compatibility and zero forward compatibility.)
DB3 (if it were to be considered) would be a new compiler and most like a significant step above DB2. For example, making it based on .NET technology (classes, object orientation, etc) or perhaps going crossplatform (Linux/OPENGL, PS2, XBOX, etc.)
Not something likely to happen for years, at best possible speed. Right now DBP (DB2) still has plenty of room to grow and areas to clean up/improve on.
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TAZ