I also have previously mentioned how many times the British Isles were invaded, and alluded to the idea that another invasion would not be historically uncommon.
However, one point was missed on me.
It seems very likely that an Islamic seizure will not yield to any future waves, either ethnic nor religious, because that is what Islam does. There might be future ‘invasions’ or migrations, but they will never supplant or become dominant.
Spain managed to kick them out in “la reconquista” - they reconquered their land from the islamists.