It is painfully clear that here in Europe, and in the western world more widely, we cannot sustain our current lifestyles. Europeans are not reproducing; the birth-rates in every European country are not sufficient to replace the population. This is the natural result of a materialist, individualistic order, where our cars and houses, technology and luxuries, are more important than raising a children. It has simply become economically irrational to have children. We are showing all of the signs of civilizational decline and exhaustion.
This will cause chaos in a number of ways. The rapidly ageing population will have to be sustained, and if the work-force has not been reproduced, we will not be able to accommodate these old people. There are two options to this dilemma. A full-scale privatization of all societal amenities and the welfare state, which is a platform on which no political party could win; or, we open up our doors to even higher levels of immigration, with the ensuing cultural and demographic changes increasing the risk of cultural conflict.
The Roman Empire was once in a similar position. They became decadent, obsessed with luxury, and completely dependent on barbarians; we are utterly dependent on immigrants, and will be more so in the future, but this cannot be maintained. The future looks bleak.