As of right now, John Cena doesn't have a WrestleMania opponent. If he manages to emerge from this Sunday's Fastlane PPV victorious, he'll obviously be WWE Champion and on a collision course to battle Shinsuke Nakamura at the Showcase of the Immortals, robbing wrestlings fans of the dream match which is, of course, the King of Strong Style vs. the Phenomenal AJ Styles.
However, as suspected, it doesn't appear as if that's the current plan. Looking at the leader of the Cenation's schedule, he's set to work RAW branded WWE Live events all the way until WrestleMania and if he was WWE Champion, he'd obviously be defending that on the blue brand. It's also worth noting that he's not currently lined up for anything AFTER Wrestlemania takes place either.
So, what does this mean for Cena? Well, assuming The Undertaker is still happy coming out of retirement, he'll be doing battle with the Deadman on the Grandest Stage of Them All in a bout many wrestling fans have been hoping would become a reality for years now. With any luck, things will start falling into place soon and we'll learn what exactly Cena will be getting up to next month.