You're talking about Egypt suddently becoming uninhabitable. That's not the case here. The case is that first it will be capable of hosting 100 mln people, then

You're talking about Egypt suddently becoming uninhabitable. That's not the case here. The case is that first it will be capable of hosting 100 mln people, then shrink to 90, then to 80, etc... Each transition will probably take five years. Of course there's a possibility of disasters there a wave of "sea people" may hit your wall.