While not necessarily his moniker, John Cena has been the franchise of WWE since 2005.
That's clearly changing, and has been for years. Roman Reigns is firmly entrenched as "the guy" WWE wants to carry their torch. He's younger, faster, has the lineage, and has been promoted at all costs over the remainder of the roster -- a situation familiar to John Cena.
We've seen Cena show up at various international shows this year in Saudi Arabia, Australia and China, but has been absent from the WWE scene in North America since WrestleMania. Even at WrestleMania, Cena was beaten down real proper by The Undertaker -- who has provided WWE with more mileage this year, surprisingly.
Cena won his most recent world championship at 2017's Royal Rumble, but his lowered profile has been going on for quite some time. In 2018, Cena experienced a large build where he repeatedly called out The Undertaker, and viewers weren't told if the match was actually going to happen until mid-way through the show. Cena, watching "as a fan," rushed to the back, changed into gear, and was squashed. Such is life.
In 2017, WrestleMania was used as a vehicle to promote the "Total Bellas" series, when Cena teamed with longtime girlfriend Nikki Bella to defeat The Miz & Maryse. Cena would propose after the match, another memorable moment.
An injury left Cena off of 2016's Mania event, instead showing up with former rival The Rock for an in-ring segment with The Wyatt Family. Cena was able to support the Rock following an impromptu match with Erick Rowan. A neat experience, another that went unpromoted due to unforeseen circumstances. That wouldn't be Cena's first run-in with Bray Wyatt, they were involved in a WrestleMania mid-card feud in 2014.
There was a title on the line in 2015 when John Cena derailed the hype train of United States Champion Rusev, who was never quite the same after the loss. As far as promotion goes, the match was arguably third or fourth down the card.
Cena's role in WWE has changed, and it had to at some point. He's developed into a successful actor, and by the time next year's show roll around, will be approaching 42-years old. Present-day booking would indicate Cena probably has about ten years of big shows left in him if Triple H, Kane and The Undertaker's trajectory are any hint, but in the case of Triple H and Undertaker, they're usually featured in highlighted, prominent spots. It's hard to believe that the older Cena gets, the less he'll be featured.
I wouldn't expect him in the same role he has been -- the full-time legend, working with the young upstarts. It's bound to happen a time or two, but it seems more likely WWE goes into "dream match" mode. But how many "dream matches" are there with Cena? We know he's capable of having great matches, but the reality is, he's had those matches with most of the roster before. With WWE's insistence on building the brand over individual talent, I wonder what kind of first-time "dream matches" could unfold. There are plenty I'd like to see personally, but highly doubtful WWE sees the crossover ability in them they so often seek.
I have no doubts Cena will remain an integral part of WWE when he's around. I don't doubt that he sees WrestleMania as a priority, and he should for several reasons. The perception he put forth that he'd never leave is dwindling in reality with each passing month.
Who are the options? Braun Strowman and Cena don't have extended history. Drew McIntyre could certainly turn into something that WWE views as special enough for the matchup, and has been appropriately protected. Samoa Joe and John Cena have never had a televised singles match, and have a wealth of history together. On the NXT side of things there are a substantial number of possibilities, but the questions of how their popularity or relevance will be sustained when they hit Raw or Smackdown.
I'd imagine along the way we're going to see our fair share of "LAST TIME EVER" matchups with Cena as well, much like we did with Triple H vs. The Undertaker at WWE Super-Showdown. With the average cameo age of WWE going past 50, John Cena is very likely to lower that and move more towards that part of his career.
John Cena is still valuable to WWE and WrestleMania, but the cash-in on that value has question marks.