If this keeps up, I have no idea how countries are going to deal with displaced migrants. We barely have the capability right now to properly deal with Syrians and African refugees.
Note that I'm talking about overall total world costs. The only reason you have refugees now is the costs are being externalized. Bombing Syria is pretty cheap if Europe pays the refugee price, not sure the last time Germany bombed Syria, but they're paying the price for someone else doing it right now... Because of the ease of externalizing costs, I suspect we will get more refugees, but reducing it would be a wise goal.
Obviously there are very small exceptions to the very large general rule, like if your whole island submerges or whatever.
They can also be relocated to cold but uninhabited places such as Siberia.