I would argue that it all really depends on what you mean by ‘threat’ and who is making it. If it means ‘the average Muslim in the European street’/‘Muslims breeding for victory in Europe’, then I think it’s nonsense - if it means terrorist threats, I think it’s very real.
However, the the latter is a sign of weakness in the Muslim world rather than strength and long-term ambition. European Muslims are at the sharp end of the shock of ‘the modern’ - something, it should be noted, that Europeans dealt with very, very badly - Communism, Fascism, Nazism, and what might be called ‘non-specific’ Authoritarianism and the catastrophe that took place between 1939 and 1945. Out of that catastrophe, came the kind of liberal/social democracies that Muslims in Europe are struggling to come to terms with.
The awful truth of ‘the modern’ is that you can’t have the goodies without compromise - something that China and India have had to learn in recent times while countries like Pakistan are failing miserably to to do so. When you have nothing, all you have left is your ‘honor’ and when you’re going nowhere, the only context you can put that in is fundamentalism - whether that’s religious or political - I’m old enough to remember the ‘Great Proletarian Cultural Revolution’ in China, for example.
The lessons are not something anybody else can learn for them, or impose on them. Fortunately or unfortunately, they can’t have ‘stasis’ - ‘the Muslim in the street’ wants a good life too. Don’t forget that while you’re rolling your eyes.