You may be right about an increase in life expectancy. However, all that would mean is that there would be more 90-something baby boomers and 70-something Generation Xers around to witness the Islamicization of Europe and the conversion of the United States and Canada into Third World nations. It is hard to imagine such people as being capable of resistance to young, vigorous Muslims. There are only two effective measures to prevent the fate that Steyn predicts: increasing the birthrate of native Europeans and North Americans and severely curbing immigration from Muslim and Third World nations.
And native Europeans are not going to start having more children soon because they utterly lack OPTIMISM and LOVE OF COUNTRY.
Think about it: these are two traits that figure deeply, although mostly silently, when people are looking at the out-years of their family.
When these two things are in place, the idea of bringing children into the world is nurtured by a general feeling of hope and that the children one has will have the opportunity to live in freedom and contribute to something that matters.