UPS and FedEx Express had firm ordered new A380 freighters but Airbus halted that version when they had those harness troubles in the early days of the passenger version. The freighter had been intended to be the base for heavier weight passenger versions and stretches as well. Only a pair of wings got built with some different high lift system.
Converted passenger aircraft might make sense as package freighters but the cabin floors are not good for general cargo and the upper deck needs new high level lifters. Maybe for express cargo? Think about all those EK A380 coming off lease. More promising than AEW or anti submarine for sure.