I'm hopeful that, assuming they will ever become a majority in Europe (well, northern en western Europe) which I highly doubt, Islam will have gone through a reformation from within the Muslim community to secularize Islam just like Christianity. Every year, more and more Muslim women are entering universities. Education has the biggest influence with regards to that secularization. The one thing we have to be wary of, and in my view this is the biggest danger of the right wing, is segregation. If we create streets or communities of one color, if we live beside each other instead of with each other, then those Muslim women will never realize the freedom they can have, by looking at, and interacting with western women. They have to realize that here in Europe, you can marry whoever you want, women are equal to men, etc. So yeah, long story short, with enough education and living with each other, I think the problem will mainly solve itself before any doom scenario of a Muslim majority happens.