I just don't think the climate is right thesedays for any band like this to follow the U2 path from arenas into stadiums. No reflection on the quality of these bands. It just can't be done nowadays. Coldplay (as much as I don't like them) probably had the best chance given their mass appeal blandness safety first approach but even that didn't work. We might never see another U2. Doesn't really matter since it doesn't mean good music is going away.
Yes, you're right. Jon Bon Jovi of all people loves to lament the state of the music business now, where (and you need to imagine JBJ using all of his acting 'ability' here to wring out the pathos) kids from the backstreets are no longer gonna be able to pick up their guitars and sell 100 million records. He's correct - piracy and legal downloads have changed things so much now that the traditional notion of a megaselling album like Thriller or Dark Side Of The Moon seems inconceivable now.
But, in terms of worldwide appeal, let's look at some of the contenders:
Coldplay - probably will make the leap to stadium success, if they keep on going the way they are. I like them; plenty don't, but it's possible to like them while remaining a U2 fan! (Chris Martin's lyrics are astonisingly poor though, so they don't really have much to 'say' in a meaningful sense). Their music is the kind of thing that's used on sports shows, charity appeals, and glossy TV dramas interchangeably, and that's commercial golddust!
Snow Patrol - think they're destined to remain a support act rather than headliners. Can write good songs but have an anonymous, generic image, and also lack a charismatic and recognisable frontman. Gary Lightbody (who I went to school with, trivia fans!) all too often hides behind his guitar, and I don't think he has a particularly expressive or memorable singing voice.
RHCP - Can't argue with their album sales or live success. They ARE a stadium act, but other than their (admittedly sizeable) fanbase, they don't have the more general appeal of U2. Plenty of non-fans would go to a U2 concert, but I doubt if non-fans would go to see RHCP on a whim.
Killers / Kings of Leon / Keane (etc) - I think in terms of popularity, all of these acts have found their fanbases and aren't going to be able to get to the mythical 'next level'.
Muse - I know that they've played Wembley twice, but I note that they're supporting U2 in N America. Make of that what you will. Despite having Stephenie Meyer as their biggest fan, I don't think they'll ever be considered the biggest band in the world.
Radiohead - a group of men who increasingly only make music to suit themselves. Why do they seem to find being in a band so miserable? Their job is basically their hobby, so cheer up, for God's sake! After OK Computer, they could've risen even higher, but they deliberately chose a more personal, uncommercial approach.
REM - Their commercial heyday is long past, although they'll always remain a reliable live act.
Robbie Williams - one for all the non-Americans. Look at his last tour - he sold out U2-sized stadiums in Europe, S Africa, Dubai, Australasia, S America, Mexico. But, his total lack of a US profile and known hatred of touring make that level of success again distinctly unlikely.
Oasis - stadium-sized ambition in the 1990s weren't carried through, but I'd argue that - within their own particular niche - they're more popular now as a live group than they've ever been. They can fill stadiums in the UK and Ireland all day long, but are probably a large indoor arena act elsewhere.
Metallica / Foo Fighters - Holding up the reputation for big rock, but - like RHCP - you really have to like their music if you're going to go and see them live.
I think that, in order to be considered 'big', we have to accept that this
means having a sizeable US profile. Conversely though, there are artists who are content with being big in America, while neglecting other territories where they have plenty of fans. Happily, as this includes such dross as Miley Cyrus and the Jonas Brothers, I think we can safely exclude them from this argument.