#1 Roman Reigns
Roman Reigns has been in the main event of each of the last four WrestleMania events, so it's probably pretty safe to assume that he'll continue that streak when WWE heads to MetLife Stadium next spring.
While putting Roman in the ring with The Rock might not be the best idea if WWE wants Roman to be cheered, but it'll definitely get a lot of eyes on "The Big Dog," which is probably all WWE cares about in the end.
The only reason why WWE might not end up doing this match is simple: the finish. Everyone would know that the younger, full-time WWE star (Roman Reigns) is going to beat the part-time guy who only wrestles once a year at most, which might cause the fans to do what they did during the main event of this year's WrestleMania.
But, in terms of possible first time ever dream matches, this might be the biggest one that WWE could do at the moment. So, don't be surprised if The Rock comes back next year to face Roman Reigns.