What if we get a loaded main event like The Shield versus John Cena, the Undertaker and Triple H?
Hear the idea out.
Undertaker could still wrestle at Extreme Rules. Maybe he'll wrestle Ambrose in a rematch from Smackdown while Rollins and Reigns go after the tag team titles. Or maybe he'll sell the injury till after Extreme Rules (this thread idea only works if Taker is to return for revenge against The Shield at some point) and allow The Shield to gloat about laying the Undertaker to rest (for the moment) before he returns for payback.
Speaking of which, WWE's June PPV might be called PAYBACK for a reason. Undertaker returning against The Shield fits in with that PPV title. I also suspect that since the Shield tried to jump Triple H once before, they'll either interfere on Lesnar's behalf in the steel cage match or attack HHH the night after. If they cost HHH the match, he could come out the next night and scream into the microphone for The Shield to just come straight at him. I'm picturing Austin's angry rant and challenge to the NWO the night after No Way Out 2002 when they cost him the title. Triple H gets destroyed and a feud between them begins. If they don't cost him the match, they could still destroy him the next night all the same.
This could all lead to a huge six man tag team main event at Payback, with Undertaker and Triple H teaming with a third partner - John Cena, I'd imagine - to take on The Shield. And the PPV name could refer to having payback on The Shield in general, as they could take their first loss here. I'd rather they didn't, imagine ending a whole PPV with them walking out as victors but if they're gonna lose, is there a bigger team than those three to lose to? The fact that they would make their first loss (as a three man unit) a big enough deal to main event a PPV also says something.