I think they are doing it to slow the pace of resignations. Hope is a powerful thing. If they know the reaction will be disappointment then they are better off delaying as long as possible. Talking about going back to the States, Europe, over to China, etc is one thing. Actually pulling the kids out of school and moving the family is another. As long as the hope of a change in rostering/pay raise is in the back of your mind you will probably delay filling out that application or going to an overseas assessment.