You could be right, but it depends if the the jack used has the sensing feature. if the headphone out jack doesn't have the 'sense' connection to the controller, then we're out of luck. if both line out and headphone out use the same jack, and is physically wired to the controller, then its possible to enable it in a future firmware update.
However, looking at the two different jacks, it looks like only the line out has the jack sensing connection. stare down into the jack and you'll notice the line out has two terminals at the very end, whereas the headphone out doesn't have anything, so I highly doubt it.