The long awaited title that every Marvel fan has been dying to see wont be revealed until after the first trailer of Captain Marvel. When Infinity War was first announced it came in as a package, Part 1 and Part 2. As the movie came closer and closer to reality, Marvel Studios decided to rename it and keep it under wraps to avoid any future spoilers. Now Kevin Feige, president of Marvel Studios, has announced that we won't be seeing the title until after Captain Marvels trailer since they are connected and are extremely important. In an interview with Collider he said, “That’ll be after the Captain Marvel teaser probably, announcing that title, It’ll be towards the end of the year with however we launch that film.”
Avengers Infinity War trailer debuted on November 29th, 2017. So we can expect a trailer to be around the same time. Regarding Captain Marvel we can expect a trailer a couple months before that, maybe September or October.