SPOILER WARNING: I can't imagine anyone's left that doesn't know the ending of Avengers: Infinity War, but still, I feel compelled to throw up a spoiler warning here. Don't read this if you haven't seen Infinity War, m'kay?
There are a lot of questions left unanswered after the ending of Avengers: Infinity War, most of which has to do with the fate of the characters who were affected by Thanos' fatal snap. There's been a lot of debate about how Avengers 4 will handle several key characters disappearing into the wind, but not everyone met their demise by The Snap. Vision (Paul Bettany) had perhaps the most tragic death of the movie, as he convinced his love Wanda (Elizabeth Olsen) to kill him and save the universe in the process, only for it to mean nothing as Thanos simply reversed time and killed Vision himself. It's a bummer of a way to go, but there is a path that Marvel can (and should) still take with the Vision.
I think that they can bring the Vision back to life, but not as audience members know him. He'll be an entirely new version of himself, with a new personality, and a new actor playing him. And we all might just have Shuri to thank for it.
An entire subplot of Infinity War involves the Avengers trying to protect Vision and the Mind Stone giving him life. However, Vision is the most technologically complicated being on Earth, and removing the stone from his head would most likely be fatal. However, Bruce Banner makes a point of saying that Vision's mind is made up of several parts and that even without the Mind Stone, there's "still a whole lot of Vision left." Only Shuri (Letitia Wright) and the resources of Wakanda can hope to separate Vision from the stone without killing him.
So, Shuri goes about removing the Mind Stone while the Avengers, Black Panther, and the armies of Wakanda battle the forces of Thanos. Inevitably, Shuri is interrupted by Corvus Glaive of the Black Order, and just before Corvus knocks her away, Shuri makes some quick, final adjustments to the Vision. The popular theory is that Shuri, being the smartest person in the world, was able to do something to Vision's programming, whether that means backing it up or even laying a trap in the Mind Stone.
For the purposes of this article, I'm inclined to think that Shuri was able to salvage some portion of Vision's programming. His body was left (mostly) intact at the end of the movie. The movie planted the idea that the Vision can exist without the Mind Stone. All of this is key to resurrecting him, but it won't be as the Paul Bettany-version we've come to know and love. It'll be as a new version of the character based on the Vision from the Young Avengers.
A little "comic book history" time: At some point in the comics, Vision is killed, and all that remains of him is his broken body and his operating system. A time-traveling teenager named Nathanial Richards travels to the present from the distant future looking for the Avengers for help. Nathaniel is destined to grow up to become Kang the Conqueror, a time-traveling villain and longtime foe of the Avengers. However, the team was disbanded at this point and all Nathan could find were the remains of Vision. So, he implanted Vision's operating system into his high-tech armor and recruited a bunch of teenagers to help instead.
Long story short, his armor eventually gains its own sentience due to Vision's operating system and becomes an entirely new version of the character, one without the experience or maturity of the original. This Vision goes on to take the name Jonas, joins the Young Avengers, dates Ant-Man's daughter, comes to terms with his existence, and is eventually killed by Nathaniel. Comics.
Marvel Studios has rarely ever adapted from the source material beat for beat, so any version of this on the big screen would likely be incredibly different, but the basic idea is the same: they can bring the Vision back to life while still having technically killed the one people are attached to forever. They get a new character for the franchise while avoiding criticism of death not having meaning. That's called having your cake and eating it too.
There are already rumors that the Young Avengers are being set up in Avengers 4. Two twin characters -- which would likely be Wiccan and Speed -- are rumored to be involved, in addition to a teenage version of Scott Lang's daughter, Cassie. (She's a hero called Stature in the comics.) If any of this does turn out to be true, it would make sense to include a new version of Vision as well. The Young Avengers, for what it's worth, would make a great addition to the MCU.
The downside of doing this would be that this younger Vision would likely have a lot of the same problems as the original. They both are two weird robot men trying to figure out what the hell they are and where they fit in. However, young Vision could tackle that from a different viewpoint than the first thanks to his unique personality. Plus, he has slightly different powers than original Vision due to his high-tech armor body.
Marvel could decide to just leave the Vision alone and let the character rest, but the pieces are on the board for a resurrection. If I really had to take my pick, I would want Vision and Wanda to get their happy ending, but there's always been a hint of a tragedy at the center of Vision thanks to that Infinity Stone in his head and the purple madman we all knew was coming for him. At least with young Vision, the spirit of the character could still live on and get a second chance to live with the humans he was honored to be among.