I need help with my mileage upgrade request...

I have CX Gold status, traveling out LAX-HKG in late April, then returning HKG-SFO in second week of May. Both upgrades still on waitlist.

After making a mock-booking for my dates above, LAX-HKG looks half full in business as of the moment. However, HKG-SFO is already about 2/3 full. On the same day, if I return via LAX, the flight is less than half-full.

I only booked SFO on the suggestion of an agent that it had more empty seats at the time of booking (last month).

My instinct tells me to go ahead and pay the $100 rebooking fee to change my return via LAX and take my chances of a confirmed upgrade from there.

But then, wouldn't that mean I would have to join the back of the queue for upgrades on the new flight? What are my chances?

Any input?