No, John Cena is no longer the face of the WWE in the sense that he is no longer the permanent centerpiece fixture that he was from early 2005 all the way until early 2015, at which point it became evident that WWE was going "all in" with Roman Reigns. Cena is still their biggest star with the greatest name value (Brock Lesnar is a decent second), however (unless The Rock returns which seems like a possibility for one more program).
In a sense, WWE has been here before. There have been transitional periods during which there was no clear-cut "Face of the Company" and perhaps the starkest one in modern wrestling history was following Wrestlemania XIX. Suddenly Stone Cold Steve Austin, who had left WWE for months under a dark cloud of controversy, was forced to retire and The Rock was on his way to Hollywood more or less for good barring one more program with Mick Foley the next year to put over Evolution.
John Cena and Dave Batista both rose to the top at Wrestlemania XXI and WWE's business boomed after a fallow period.
What needs to be remembered, though, is this:
Cena in particular had something of the luxury of having a double-decker roster packed with some of the greatest names in modern wrestling. From The Undertaker during Cena's "Thuganomics" period to The Big Show, to Chris Jericho to Kurt Angle to Eddie Guerrero to the revamped JBL (included due to his indispensable role in putting Cena over) to the likes of Triple H and Shawn Michaels, whose consecutive performances with Cena at Wrestlemania XXII and Wrestlemania XXIII were critical in ushering in Cena's era "for good" as well as the major role Edge played in serving as Cena's most loathsome antagonist, who was able to assist Cena by being, for a while, at least, such a hated heel.
Cena had a rich roster through which to travel, and WWE made it undeniable who the top dog was, aside from Cena's rivalry with Batista, beginning with Batista defeating Cena at Summerslam 2008--though that finish was paid back seemingly fivefold in 2010, as Cena again and again defeated heel Batista.
Roman Reigns's biggest foes have been, clearly, Brock Lesnar at Wrestlemania XXXI, Triple H at Wrestlemania XXXII and The Undertaker at Wrestlemania XXXIII. The first match resulted in Seth Rollins emerging on top with the championship with the first-ever Wrestlemania Money in the Bank cash-in. Just being in the ring with Lesnar and taking the punishment Lesnar dished out on that night--I was there and while one can quibble with the process of why this is so, it must be admitted that Reigns/Lesnar had a "big fight feel" to it so it's not like Reigns appears completely out of place at the top of WWE's annual supercard vying for the top prize--had, to some degree, the desired effect of elevating Reigns a little bit, all while holding off on him becoming champion himself. By the time WWE went through with Reigns for good at the next year's dismal Wrestlemania, against an old and part-timer Triple H who was clearly there to drop the championship to Reigns, a good deal of his momentum had fallen flat, and to be sure much of that is due to WWE's booking and Reigns having considerable struggles with his babyface personage.
The match with Taker was apparently a bit underwhelming but at least Reigns went over. The next night's Raw displayed a ruthless crowd giving Reigns all of the jeering they could muster and he took it like a man.
Reigns's booking with the Braun Strowman feud has been... Intriguing. It's good to see the hunter become the hunted, something the Reigns character needed.
At this point it feels inevitable that Reigns/Lesnar II is penciled in, probably for Wrestlemania XXIV, in the very venue where Lesnar broke Taker's Streak, a mere year after Reigns retired Taker. Obviously Reigns more or less has to go over in this case.
Whenever we finally get Reigns/Cena (WM 35?) it will be fascinating to see how WWE puts it together. My hunch is that Cena, a part-timer nearing the end of his in-ring days, will be the grizzled and, even by marks who have claimed to hate him, respected figure against pushed and pushed again Reigns. As curious as it is to admit it, Reigns/Cena is quickly becoming one of the few potential big-time matches WWE will have in its quiver following Reigns/Lesnar II. As for Strowman's push, a large "To Be Continued" sign must hang over that project.
As heavily pushed as Reigns has been over the past three years, he has not wrested the "Face of the Company" designation for himself, and with Cena only periodically around, that mountaintop summit remains vacant for now.