The demography of Europe won't change at least not in 1-2 decades. There are many reasons behind it.
1> Today, There is no leader like Hitler or Mussolini who believes in expansionism nor any Today's Chancellor, PM or President has ultimate right due to diplomacy, democracy and fear of WW1,2.
2> Today there are basically 3 powers in Europe. U.K., France and Germany. All 3 are powerful enough and they don't have any dispute. Divided Europe is not good for U.S., so U.S. won't allow such things. During WW1 and 2 majority of European countries were not with U.S. which is opposite now.
3> Historically Developed nations are always more intelligent than developing and semi/un developed nations. Today out of 40-50 developed nations, No country has hegemony mindset except U.S. (that also because It's Super power and nature of diplomacy). Japan was super power till WW2. Today, Italy, France, Germany, Japan, S.K., Australia, KSA, U.A.E., Canada are not interested in any war. They just believe in creating stooge for vested interest. They control more precious things i.e. Money and Diplomacy.
3> Many people say Germany is suffering from U.S. and U.K./France oppression which is completely wrong. As of now, Germany is 3rd largest arms exporter in the world after U.S and Russia. Their economy is very strong and even they have surplus trade with PRC. Today, Germany won't be that strong if that would be the case. They are never in limelight because they never ruled the world like Spain, France, U.K nor they want any more. They only ruled 2/3rd of Europe and even today Germany has far big influence than rest of his counterparts combined in few countries like Switzerland, Austria, Hungry, Poland. In Short, Today Germany is very strong and they don't have any desire for war. They already ruling 1/3rd of Europe, Strong economy, helping 10+ countries by Aid/Bail-out and 50+ countries are buyers be it Technology or Military weapons.
Europe will remain intact for long long time to come. Only Asia will be face the consequence due to too much differences.