/usr/bin/python should never point to Python 3. Because of the compatibility break, the convention (and default for the Python build scripts) is to always name

/usr/bin/python should never point to Python 3. Because of the compatibility break, the convention (and default for the Python build scripts) is to always name the Python 3 binary python3, so there should be no conflict. It's understood that during the (very long) transition period there will be need to run both side by side. A handful of ditros have gone ahead and named it python anyway. A stated motivation has been to encourage adoption of Python 3, but practically they're just shooting themselves and their users in the foot, and ensuring incompatibility with the shebangs defined for every other OS. (I don't think there's any plan to ever switch the default binary name from python3 to python, so this incompatibility may never be resolved.)