That seems questionable. Currently a lot of passenger airlines are retrofitting their widebodies to carry cargo instead. And the quick and easy solution is just removing the seats and carry a few extra crew as smoke warning system. In fact, from what i can see, freight rates are already sliding slowly back and that will increase, therefore the pressure on the cargo market will increase, considering that the large passenger airlines also do cargo business on large scales, i guess the integrated model will probably survive, although the pure cargo carriers have it easier in the short run, but probably more difficult in the long run.