Your last two predictions are far-fetched in their cynicism. If it gets to that point, the laws will be irrelevant anyway. As it stands today, the migrants are far from the dregs of their own societies. With a bit more enforcement and coordination the boats would stop coming. Presumably the numbers will rise but the genuinely desperate climate refugees of the future will always be going to the first nearby country where they are safe, not halfway round the world to the place with the best economic prospects. Not claiming that any of this is fair, but then the tribalism that you mention is also what makes the cohesion of our societies. People will always resist being overrun from the outside, and that will not make them fascist.