Perhaps the one thing Marvel fans want more than a Captain Marvel trailer or to see Ant-Man and The Wasp in theaters is to know what Avengers 4 will really be titled. That will probably be coming pretty soon because things such as the title will likely be in the hands of places Marvel doesn’t completely control (licensees), and it’ll leak if Marvel doesn’t officially reveal it before. However, I have been able to confirm what the title was internally for a very long time.
Through multiple sources I’ve received confirmation that throughout production, they really were referring to the second half of Thanos’ story as “Infinity Gauntlet”. That explains why people such as Frosty at Collider were so adamant that it was called Infinity Gauntlet during the Infinity War press junket. He hammered the Russo Brothers on it in a video interview, and then did the same to Kevin Feige who denied it was the title.
Throughout filming that’s what they were calling the movie, but as everyone knows the title accidentally was blurted out at the Guardians of the Galaxy Vol. 2 premiere. That’s why they were so quick to jump on it and try to put out the fire.
Whatever they end up calling the movie, it probably won’t be as perfect Infinity Gauntlet. That title doesn’t just reference the metal glove on Thanos’ hand, it has a double meaning. It also describes the Gauntlet that the Avengers fight their way through the Infinite reaches of time and space in the quest to prevent what Thanos did in Infinity War where Thanos is trying to stop them every step of the way.
Honestly they should’ve just stuck with the title despite it having accidentally been leaked by one of the cast members. They’ll come up with a good title, but Infinity Gauntlet is really the perfect one for what happens in the movie.