So long as France has such a generous welfare state, they will need young workers to pay for all of those 55-year-olds that retire with full government benefits. With people living until they're much older, and with the French not having children, France will be forced to allow increasing numbers of immigrants. Maybe more of those will come from Eastern Europe, but I think Algeria will continue to be France's #1 source of young workers (remember that Eastern Europe's birthrate is well below replacement level).
I hope I'm wrong. Western Europeans have proven to be wholly incapable of standing up for Christianity during the past 50 years, and Western Europe will have Sharia law if Islamists (such as most Algerian immigrants) become a majority or even a large and noisy minority in France, the Netherlands, etc. (And when Western Europe adopts Sharia law, just think about what Justice Kennedy will be citing in his opinions.)
Dane told you to stop after I got the last word in. No fair!