The Royal Rumble hasn't even happened yet but Dave Meltzer from the Wrestling Observer Newsletter believes that the two main events for Wrestlemania 34 are practically set in stone at this point.
The first one, is a match that almost every wrestling fan with their finger on the pulse has seen coming, Roman Reigns vs Brock Lesnar and the second is the much-touted match for John Cena, but who will his opponent be?
Right now, the two top matches for Mania are scheduled as Lesnar vs. Reigns and Cena vs. Undertaker. So unless Undertaker changes his mind, and given how hard they promoted him for the 25th Raw and his being backstage at TV in Birmingham on 1/9, it makes that seem unlikely, one would expect the angle for Cena vs. Undertaker to be shot in two weeks on the 25th Raw.
It looks like the WWE is finally pulling the trigger on the Undertaker and the much is practically guaranteed to happen given The Undertakers appearance backstage at a recent SmackDown LIVE and his hyped appearance for the RAW 25th Anniversary Show where he is due to begin his feud with Cena.
The other thing worth noting is that this means Cena won't be in a title match at Wrestlemania so he won't be beating Ric Flair's record any time in the next few months unless he wins the title and then drops it again (which is highly unlikely)
It's also unclear whether or not Brock Lesnar vs Roman Reigns will be for the title, but there's a strong chance that it will be because if Lesnar loses, even if it is in a Triple Threat match against Kane and Braun Strowman where he doesn't take the pin, the Reigns match becomes instantly less desirable.
This also means that John Cena, who is, or was, currently the favourite to win the match, is unlikely to be winning the Royal Rumble match, as he doesn't need to to have his match with Undertaker.