First off, it's important to remember that Vision has been one of the MCU's best late entries ever since he soliloquied into our hearts during Age of Ultron. Fans love him, and Bettany seems enthusiastic about keeping the story going for as long as the paychecks clear. "I love Vision. Yes, I'm in," he told Esquire recently when asked if he'd keep playing the character forever — so there's no real reason for Marvel to throw the synthezoid out now.
What's more, the studio has plenty of comic book backstory to draw from if they want to explore Vision's potential return to his former self. The desaturated version of the character had a long journey recuperating from his deconstruction, including a stint disguised as a regular dude called Victor Shade as he tried to re-learn how to be a human being. Combine that with the Marvel Cinematic Universe's newly ignited love affair with the Multiverse, and there are literally limitless ways for Vision to return in one form or another.
More than that, the "robot strives for humanity" story is a science fiction classic for a reason, and it's one that would fit into the MCU perfectly. It gives the audience a prefab fish out of water to root for, while opening the door for conversations about the nature of morality and emotion. A Marvel universe that leaves White Vision wandering and unseen indefinitely would be an enormous waste of potential. In short, it stands to reason that he'll say hello again.
