Is John Cena getting ready to make an appearance at WWE WrestleMania 37? Triple H certainly seems to think so.
Speaking with Sports Illustrated's Justin Barrasso, WWE's Executive Vice President of Global Talent Strategy & Development suggested that the 16-time World Champion may indeed be on his way to Tampa, Florida on 10-11 April:-
“I won’t put words in John’s mouth, but I can speak to his passion, and it’s WWE and WrestleMania. Once you do this at a high level, and John does it at the highest, it’s very hard to put down. If there is a way for him to be there, he will be there.”
That's about as close to an outright confirmation as you're going to get from a WWE official prior to a company announcement, though it should be stressed that this isn't yet an outright confirmation.
Cena hasn't been seen in WWE since WrestleMania 36, where he worked Bray Wyatt in a wild Firefly Fun House match that systematically tore down everything fans have been complaining about regarding John's push and presentation over the years, drawing widespread critical acclaim in the process. Given his in-universe existential evisceration, it'll be interesting to see what form he might return in at WM37.