Oh, I forgot to mention earlier:
Attach Luxembourg to Flanders-Netherlands
Merge Austria, Germany, and Liechtenstein.
The Duchy of Luxembourg doesn't border either Flanders or Netherlands.
This being said, the day Belgium splits up, I'm there to throw molotovs at every cheering Flemish/Walloon nationalist who's cheering in the streets. There will be riots: because of this stupid unimportant issue no one can agree on, Belgium still have got no government 4 months after the election. There are more important things to tackle.
OT, I see more nations joining the EU, especially to the east (Turkey, former Soviet nations, maybe even Russia), and countries like Norway, Iceland, Greenland, etc... will feel forced to join as the EU gets bigger and bigger.
More EU countries will see the benefits of the as well. and as it will be used in more and more countries it will have a stronger impact on the international market. I don't think the $ will disappear though.