While promoting Captain America: Civil War, Joe & Anthony Russo confirmed that Avengers: Infinity War Part 1 and Part 2 would eventually be retitled, citing the need to denote the fact that the two films have very different storylines. Perhaps they meant they were going to drop the subtitles altogether rather than replace them with something else?
As the various Hollywood trades such as Variety, The Hollywood Reporter and The Wrap reported on the Brie Larson casting news for Captain Marvel, Deadline Hollywood's report had something extra, the fact that the Avengers: Infinity War Part 1 has been retitled Avengers 3. It's simple but it doesn't convey the same level of excitement that Infinity War does. But a lack of subtitle certainly didn't prevent Iron Man 2 or Iron Man 3 from cleaning up at the box office. What do you think of the new title?

也就是不分上下