We recently found out that John Cena will have a big match at WrestleMania 34, and now there's rampant speculation that it might just be against The Undertaker.
Despite initial reports that Cena would actually be facing AJ Styles (possibly for the WWE Championship), Wrestling Observer’s Dave Meltzer reckons that we may actually see the "Franchise Playa" go one-on-one with The Phenom on the Grandest Stage of Them All.
Of course, 'Taker was "retired" by Roman Reigns at the last 'Mania, so even if WWE does decide to reverse that, there's a very good chance just as many fans will feel cheated by his return as they will excited by the prospect of it.
At any rate, this is just a rumor for now, but if they are looking for the biggest WrestleMania opponent possible for Cena, this would be the way to go.