Islam is a death sentence, regardless of what anyone thinks of the ideology, for very clear and demonstrable reasons it will cause society to fail.
Unlike Christianity, it cannot be changed and adapted to suit the values and culture of the host country, that is expressly forbidden.
The shift towards polygamy and marriage at a far earlier age will erode the foundations that made European society so successful, and the shift from an individualistic society that values free expression and self-determination to a collectivist, tribal society will gut industry and innovation.
Islam has some merits, but they're almost incidental, and it only works well in the environment that it was expressly designed to dominate, which is an iron age tribal setting. Its scope is so limited partly because of how specialized it is, Mohammed created a tool to facilitate his own conquests, and it has little application outside of that.
Europe is going to go one of two ways, either governments will be elected that will remove Muslims through law, or they will stick their heads in the sand for too long and it will become Serbia 2.0.
Muslims do not mix, ethnically or culturally, they do not intermarry as they see non-Muslims as less than dirt. They establish their own states within states and try to carve out Islamic territory when their numbers get high enough. You can see the precedent in every single country that has had its Muslim population reach around 30%. Bosnia, Chad, Lebanon, Albania, Malaysia, Sudan, Bangladesh, Indonesia, Morocco, Pakistan, Syria, etc.
They don't bide their time and let demographics do the work, they have a habit of blowing their wad too soon and drawing far more fire than they can actually handle, which is happening with the Buddhists in Myanmar as we speak. The same will happen in Europe in the coming decades.