[B~E]

Each State is a special case. For exemple, the only reason Turkey is not an islamic State is because of the legitimacy inspired by Ataturk's nationalist legacy, which give an sécular alternative to an all-encompassing sharia rule, and the fact that the army is ready to ensure that this sécular alternative stays on the table at any cost. So without those two factors, the army and Ataturk, I really dont see on what model would Turkey's muslim population and its Tiny Minority of Extremists™ base its government. Why would it be any different from any other country where muslims are the majority?

Of course, Germany would be a different case, in no small part because, like you rightly pointed out, of the dynamics between the different minority groups, may they define themselves as religious, ethnic or ideological.

But if our contemporary world is any exemple, this dynamic is nothing to look forward too. Like I already said, no nation-State has anything to gain from becoming a heterogenous cleft country.
So the 100$ question is, can liberal Western institutions witstand the pressure of a muslim assertiveness that will increase along with a growing demographic presence?

Beats me, I dont know. I dont really care specificaly about Christianity or Islam, it doesn't seem necessary to discuss the article from the religious angle. To be honest, my take on it concerns the (in)validity of immigration as a solution to a very real demographic problem, the sterility of the debate surrounding said problem, and maybe, if I'm in the right mood, I could also jerk to the consequences of it all, such as the aches and afflictions of a society that fails to give a common sense to its populations living within it.