It's really not hard to grow faster than Christians when they are loosing members at a rapid speed.
So as long as non-believers are growing much more rapid than Muslims I'm really not scared. Especially since the extreme side of Islam doesn't even try to get a political foothold. So until then I will watch the non-Muslim far-right with a lot more suspicion and concern.
But yes, there haven't really been any attempts to get involved politically yet.
There the far-right definitely is far more dangerous.
But it surely is a topic we shouldn't ignore.
Ignore? No, but there's no reason to put this out of proportion.
First of all, Muslims are a very broad group with at least as many subsects as Christianity. Nationality and heritage also plays a huge role with Migrants, so yeah "Muslims" itself don't worry me. Some radical subsects? Sure they shouldn't be ignored and the proper democratic tools should be used to keep them under control.
The projected growth trend also don't bother me to much as I don't see Islam as anything special compared to other similar religions. The same reason why local people have less and less children can easily apply to Muslims as well. Notably access to proper health care and education. At the same time it's also important to understand that in that regard of course Muslims also aren't one uniform group. People who are registered as Muslims vary from the ultra orthodox to the "just in it because quitting is to much hassle" as Christians. Muslim children for sure are also no special in regards to them keeping faithful. They have the same "problem" with Children having their own mind and not always do what their parents want. Especially since they are in a society which actively promotes individuality.
So for now, the best way to counter the extreme portion of Muslims is rather similar to counter the national right-wing extremists. Provide them with good opportunities to have a happy life and the radical won't have ground to plant their seed.