I wonder if any other airline will take possession of them once QF are done
No one
Sold for spare parts - too big for any operator other than EK but they are likely to not want them either.
EK CEO has even said they are not interested in used A380 from other airlines
Reasons given are potential reliability problems and configuration differences.
Maybe souvenir hunters using FF points?- cabin trolleys, toilet seat, first class seats, cutlery, and other nick nacks, piece of the aluminium hull
Well that's particularly great news to EK, SQ, BA etc who will no doubt be needing the parts as their fleet starts to age.
Availability of spare parts is not going to be the factor that keeps these behemoths flying - see QF decision re A380.
why can't they be economical for freight?
According to some:
There is a mismatch between volume and weight.
The A380 was apparently optimised for passengers unlike the 747.
Potential volumetric payload would be massive. But then we come up against the same issue - A380 massive passenger capacity didn't work either.
There is a reason why ultra large freighters dont exist in significant numbers.
Airbus decided that re-engineering would have been too expensive. so the A380F never materialised.
In other words (and again) - it is too big.