I don't see it happening. Him or Roman will be champion by that time and there is honestly no way they face off at mania after all the time they've already faced.
I feel like SD will win the rumble again I'm not saying they would face each other but I wouldn't be shocked if AJ or Naka won it.
But knowing WWE I wouldn't be shocked if they went the petty route and had Cena win once again to keep the number of winners low and to start off Cena vs Roman.
unless they have roman win at philly once again to take the title off cena at mania LMAO
so I'm going with Cena, Naka, Styles, or Roman.