OpenCV, in general, tries to conform to C++03, and the latter doesn't allow a comma after the last enumerator. That said, I'm inclined to keep them, because:

1. it doesn't seem to be a problem for the current compilers;
1. it's allowed by C++11, so it shouldn't be a problem for future compilers;
1. they are, in fact, very handy for reasons @alalek stated.