Bray Wyatt vs Ryback - This one is pretty much a guarantee, even if the match hadn't officially been added to the card yet.
The New Day vs Cesaro & Kidd for the Tag Team Championships - Yeeeaaahhhh. Hopefully they make this one a 2-out-of-3 Falls match and give them twenty minutes to go out there and electrify the crowd.
Nikki Bella vs Paige vs Naomi for the Diva's Championship - I don't know if this will turn into a triple-threat match for sure since WWE generally (but not always) doesn't like putting two triple-threat matches on the same card. However, it makes sense - Paige has yet to receive a shot at the title that she won a battle royal to earn, Naomi isn't done with the Bellas and is still gunning for the championship (and lost at ER in large part because of Brie's interference), and Naomi was the one who took out Paige and prevented her from getting the title match at Extreme Rules in the first place. So there's a point of contention between all three women.
Sheamus vs Dolph Ziggler - This one's pretty obvious, especially given the name of the PPV is 'Payback.' This may or may not involve having an extra stipulation attached to it.
Something Involving Barrett And The Vacant Intercontinental Championship - It's probably a safe bet that Daniel Bryan will be stripped of the Intercontinental Title since he isn't advertised for any more shows until late June at the earliest, and since Brock Lesnar is apparently the only superstar allowed to leave with a championship for more than 30 days without defending it, Bryan will likely be forced to vacate the title and a battle royal will probably be held to crown a new champion. Instead of just your usual standard battle royal though, I say add something different to it by lifting the same idea they used when they resurrected the title back at Judgment Day 2003 - make it so that only former Intercontinental Champions are allowed to enter the battle royal except for one exception. Back then, that exception was Booker T. (which is fitting, considering he does commentary now and can give us a little history lesson in this regard.) Here, the exception could be Neville. That could get you a good battle royal between guys like Barrett, Neville, R-Truth, Stardust, Axel, Kofi, Big E, and Ziggler. Then again, this leaves people like Bo Dallas, Damien Sandow, Luke Harper, Eric Rowan, Xavier Woods and maybe even Dean Ambrose out in the cold doing nothing when they could easily add some more meat to the match, so perhaps a standard battle royal would be better, but it's an idea.
Dean Ambrose vs Big Show - I don't know how likely this one is, but neither guy doesn't seem to have anything else to do (except for the IC Title battle royal, of course), and given that the Smackdown main event for tomorrow night is Dean Ambrose vs Seth Rollins (and that can't be construed as spoilers on my part since I'm not giving away the actual results of the match), perhaps it's a sign that they're about to revisit Ambrose's feud with The Authority soon.
Add in the triple-threat WWE Championship match and the I Quit match for the United States Championship, and you have a pretty damn good card!