If I say European nations and Arabic nations don't need to change their belief in 50 years?

Europe is a big place. A big place full of empty cathedrals. My part of Europe (Scandinavian peninsula) is officially Christian the overwhelming majority of the citizens are now atheist, deist, Pagan or Heathen (our original, prechristian faith). I don't see that changing any time soon except for the mass exodus away from foreign faith systems from the Middle East to continue unabated. If you want to see a truly Christian or Muslim majority anywhere in Europe you're going to have to go to one of the very poor countries. Many of the rest of us are glad to be rid of that particular deity and return to our much older traditions that are actually relevant and native to our cultures.