Meaning that after the EU finally truly federalizes, you'll have people debating what to do if (for example) Italy decides they want out.
Won't be a problem. The idea of an EU-like union is relatively new, and the member states all have centuries and centuries of independent history. If the new treaty gets ratified, EU will have a mechanism allowing member states to legally leave it if they choose.
Anyway, I don't have problems with secessionism if it is done in a civilized manner and both sides reach a compromise. Example:
Czechoslovakia, 1991
Slovaks: "Yeah, revolution and democracy and all that stuff is all very nice, but it ruined our industry!"
Czechs: "That's because your "industry" was all heavy stuff used to produce weapons for the Russians. It had to go."
Slovaks: "Look who's talking, the snobby Czechs with their low unemployment and higher living standard. Screw you, we want to divide the federal budget fifty-fifty. Half for you, half for us Slovaks."
Czechs: "Have you gone mad?! You have 1/3 of our population and produce less that 1/4 of our national income, how the hell can you expect you'll get 1/2 of the earnings?"
Slovaks: "Either you give us that, or we'll declare independence!"
Czechs: "Fine, go!"
Slovaks: "... Uhm... *cough* On a second thought, perhaps some sort of confederation short of actual independence would be..."
Czechs: "You're still here? Get the hell out already!"
Sorry... didn't mean to support the breakup of the communist bloc.
I know how heartbroken you were over it.
Commie bloc? Me? Heartbroken?
....
No, I was talking about something completely different, but never mind.