I would suggest paying if you want it that badly!
There are never any guarentees of upgrades, I am gold and have received a good few from J to F and Y to J, but again, like others only when the flights have been full.
I have flown lots with EK over the last few months and have nOT seen a full flight nor have received an upgrade!
Congrats on the wedding. Be sure to tell the purser, as I am sure you will receive extra special attention!