1 - The Rock vs. Roman Reigns

Unless Shawn Michaels is willing to come back and wrestle The Rock, a match between "The People's Champion" and Roman Reigns is the way to go.
If The Rock is willing and able to come back next year, he probably won't be willing to come back for anything less than the WrestleMania main event, which likely means that he'll end up in the ring with Roman Reigns, who has main evented each of the last four WrestleManias.
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On top of that, The Rock is one of the few guys who could probably get the WrestleMania crowd to care about a Roman Reigns match, as they're typically uninterested in anything that has to do with the current WWE Universal Champion.
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