Cargolux
Cargolux already have an operation at STN so it makes sense for them to move there if and when Manston closes.
I wonder where Saudia Cargo will fly too as they have already announced that they are ceasing operating from Manston at the end of April but apparently they have said that it was the airport of choice for there customers primarily bringing in fresh produce from Kenya so maybe LGW might get this service if Saudia Cargo wish to retain their cargo flights to the south east of the UK.