According to undercover.com, Paul McCartney will be performing with U2 at Live 8:
"The historic Live 8 event will open with a first time pairing of U2 and Paul McCartney together performing The Beatles 'Sgt Peppers Lonely Hearts Club Band'. U2 will appear wearing the multicoloured military-style suits worn by the Beatles on the 1967 album cover."
And you just know they'll pull it off somehow. But I hope they'll be more careful with the suits than they were with their Joshua Tree clothes.