With some obvious exceptions, the past few OzzFests have been very... meh...
I think, with a break last year, it needs to go back to formula. I mean 2 proper stages, with Second Stage being for rising stars in the Metal/Rock World and Headlined by an established band that does well on an intimate stage (i.e. Rob Zombie, Slipknot, HIM). The Main Stage needs to be revitalized. I'd like to see the Headliners be Black Sabbath or Ozzy and supported by other great, established bands that have a history of incredible stage shows (again, Rob Zombie and Slipknot come to mind as perfect examples, as does Marilyn Manson).
The problem is, though, a lot of bands that would help to rejuvinate OzzFest are busy during the summer. Rob Zombie has his "Lords of Salem" film coming, as well as a potential tour. Slipknot and Slayer are busy with the Mayhem Tour. Marilyn Manson will (most likely) be doing his own thing this summer to promote Born Villain. Who does this leave?
Well, HIM is a favorite of Ozzy himself, and an obvious choice to headline Second Stage. They could realistically have a spot on Main Stage, but they perform much better in the intimate settings that the Second Stage present. They are working on a follow-up to Screamworks, so a summer tour to begin promotion for that is a very real possibility.
Guns N Roses is a clear choice to co-headline Main Stage. As of right now, they have no summer plans, and with the HOF induction stirring-up rumors of a proper reunion, what better stage than OzzFest to re-introduce themselves to the Metal/Rock Community?
Judas Priest is another band that comes to mind. Although they seem to have the early-summer planned out, OzzFest seems to begin later in the summer every year.
MSI is another incredible band that could easily headline Second Stage, or secure a spot on Main Stage. They're always entertaining and have a very devout following. They do have a spring tour lined-up, but nothing for the summer... yet.
Linkin Park could easily grab a spot on Main Stage (if not co-headline). With no new LPs released since 2010's A Thousand Suns, they seem like a stretch. But, I think they've entered the part of their career where they could tour with the impressive library of tracks, and nobody would say boo about it.
What about Eminem? Yeah, he's a rapper, I got that. But he really would grab attention as a choice, wouldn't he? And, metal-heads seem to dig him (well, my metal-head friends). He's a talented artist who has always seemed like a rock star in a rapper's world. While he hasn't released anything since Recover in 2010, he's known for touring just because... well... he's Eminem. I think it's a long-shot, but not out of the realm of possibility.
The point I guess I'm trying to make is that OzzFest needs to be given the ever-popular "reboot." Yes, traditional acts would suffice, they need to throw in some "left-fielders" to grab the attention of their waning audience.