Well, he's not going to keep his crown for the king of rock and roll forever. Even without the movies, He'll be blindsided by Fire!, Pet Sounds, and Sergeant Pepper's Lonely Hearts Club Band just like most of Rock's mainstream, as well as with the likes of Mountain, Blue Cheer, The Doors, and Iggy Pop and the Stooges. He won't do Woodstock or Altamont. More than likely, unlike James Brown, he won't do a USO show in Vietnam. Either he goes country and gospel full time by 1968, or the mods and progressive rockers stay cool longer (because his continuing career and rockabilly sound combined with his increasingly reactionary politics will either discredit the London and L.A. flavors of Punk and Psychobilly, or else cause the rise of Speed Metal ten years early, and possibly butterfly the career of Brian Setzer something fierce.)
It's far easier to boo a living fifty-something Elvis who is even more of a dinosaur than his contemporaries Roy Orbison, James Brown, and Little Richard off the stage, than it is to heckle a velvet picture of him and a crackly phonogram of "Battle Hymn of the Republic," or "I Can't Help Falling In Love With You" with an American Flag and U.S. Army Ensign both at half mast.