I think that peace is the most important issue for the future of Europe.
Europe would be even more diverse than it is now with borders that can remain open to other people because all countries in the world are prosperous and politically and economically stable enough to send millions of migrants to Europe.
All people are satisfied with European politics, as there are no problems that threaten peace between other countries and therefore also within Europe. All countries in the world are democratic, even if there are differences in politics, other countries (and them) are not sympathetic about their ideologies and spread.
Climate policy will also be an important issue where all countries are involved and fight for the environment together. This theme is about bringing the world together for climate action, which is even more important in the future!