Why he might be dead: In addition to being in the scene where Negan kills someone, the villain shows a lot of attention to Carl before the beating goes down, calling him a "future serial killer" and making fun of his eye.
Why he might not be dead: The reason Negan shows Carl so much attention likely has to do with the strange, unique friendship that the two later develop in the comic books, which showrunner Scott M. Gimple said will come into play next season in some way. On top of that, the first-person perspective of the camera isn't obscured whatsoever — wouldn't we have to see some kind of patch situation going on if it was Carl looking up at the wrong end of Lucille? Additionally, before Negan bashes in the brains of the unknown character he tells everyone to stay still, and if they don't, "Cut the boy's other eye out and feed it to his father." Negan could totally force-feed Rick this unpleasant snack before beating his son to death, but we wouldn't bet on it.