The transformation of developed societies - either into old folks' homes (like Japan) or semi-Islamized dystopias (like Amsterdam, Brussels, etc) - will lead, in fact, to emigration. A young German or Japanese circa 2040 will have no reason whatsoever to stay in his native land and have most of his income confiscated in a vain attempt to prop up an unsustainable geriatric welfare system. So many will leave. Where will they go? At one time the obvious answer would have been America - but Good King Barack seems determined to saddle us with the same unaffordable entitlements that have scuttled the rest of the west.
Mark Steyn briefly comments here about the "demographic deathwatch" on Japan, similar problems regarding population loss in Canada, and how even a few liberals are starting to understand the truly frightening results of ZPG.