U2 will never "break up". They are way, way past "break up" (much like REM). One day they'll just record their last song, play their last gig, and that will be it. They're already a part time band as it is, and it's pretty clear that being a member of U2 is no longer the full time priority of any of these guys (at least until they tour again)...and hasn't been for some time.
That doesn't mean one of them (probably Larry) might not leave the band some day to do something else. But in that case, U2 would still call themselves U2, assuming they chose to go on. But "break up"? No...that's what rock bands do when they have creative differences, are smashing up hotel rooms or each other (usually both) or they just get so whacked on drugs there's no going on.