I'm batting on 33% for J to F upgrades out of 6 segments so far this year. Not sure if being Qantas Platinum (flying QF Coded/QF Ticketed itinerary) helps, or maybe there's some truth to the first letter of your last name thing.

One op-up (first ever flight on EK metal) was at the gate and I did notice a couple of empty seats in J, last minute no show's perhaps?. The other was in the lounge when I asked (as I was headed to the gate) if the flight was looking very full.