#2 Having Cena go long in the Royal Rumble match

Too predictable.
That's the problem with the Royal Rumble match at times, and although the company can sometimes remedy this with surprise entrants, shocking eliminations, and a out of no where winner, there are other occasions where that's the not the case. In fact, there are sometimes where WWE seems hellbent on just doing things by the book!
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The problem with that however is that the overall match, which is supposed to serve as a kick off for WrestleMania season, ends up becoming a predictable nightmare that fans can't wait to be over. Again, this isn't always the case, and sometimes WWE is able to pull off legitimate shockers, but they don't have a great record at it during the Royal Rumble.
One thing that adds to the predictability of the match is when superstars such as Randy Orton John Cena and other well established superstars end up lasting a long time in the match. While this can sometimes serve to make the eventual winner look even better for defeating the established star, it also takes the spotlight away from others that could be there.
For example, let's say it could either come down to Seth Rollins versus John Cena or Seth Rollins versus Dean Ambrose. Although some might see Cena versus Rollins as the better moment, especially since Rollins eliminating him would be a big deal, it ruins the opportunity for WWE to put Ambrose or even someone else in that spot.