Bug 7450 fixes so that we respect the default audio device settings when connecting. However we don't respect any changes after that, which we'd ideally like to do.
One scenario is a user connects and starts working. Later they want to listen to music so they connect their USB headphones and switch their settings to that device.
Another scenario is that they later plug in a microphone because they want to join a teleconference meeting.
This change seems to require upgrading to a later PulseAudio as it has more flexible handling of changing default devices.