OK, I finally managed to get into my booking for the upgrade.
It's less expensive DFW-BNE than SYD-DFW (my booking connects at BNE with a domestic flight to MEL) (45K/72K) so I decided to go ahead and request.¹
It's showing
J9 C9 D9 I9 W9 R5 T0 ... with 9 unallocated F seats in Business Class and 6 unallocated Skybeds in PE; so chances are reasonable for a seat upgrade.
¹
The Upgrade Zone Cut off is 8400 miles; SYD-DFW is 8,578 miles and DFW-BNE is 8,303 miles, even though the schedule has it ¾ hour longer (Great Circle Mapper)