I would be a little more generous and give a 1% chance. There are always exceptions, and happily I was the recent beneficiary of an OpUp from Y+ to J on a rammed QF flight.

Even allowing for an oversold Y/Y+, my situation was borne out of exceptional circumstances given the large quantity of re-printed J and F boarding cards waiting at the gate for the lucky ones. My point is that even an oversold cabin on QF may not be enough to get you moved up with your OW status.

QF are very tight on giving out opups, so best prepare to travel in the cabin for which you are ticketed.