Back in May, directors Anthony and Joe Russo announced that the next two Avengers movies would not be Infinity War Part I and II as originally detailed, and that they were "very different films". Now Disney and Marvel Studios have officially confirmed that the first of the two will simply be known as Avengers: Infinity War.
As for the other? No one is saying just yet. For now, the movie is saddled with the moniker Untitled Avengers, which we presume is a casualty of Marvel's internal story team (including the Russos and writers Christopher Markus and Stephen McFeely) changing things up when it comes to the tale they're telling. You've got to figure that the second film will still be dealing with Josh Brolin's Thanos to some degree, but it appears the story will not quite be one giant narrative across two movies.
All we know for now is that it will indeed feature Thanos finally arriving to try to conquer everything in sight, with whatever version of the Avengers and a group of other heroes (Benedict Cumberbatch's Doctor Strange and Brie Larson's Captain Marvel most likely, plus potentially some of the Guardians Of The Galaxy gang), teaming up to fight him as Alan Silvestri's music plays.
Of course, it's all moot until here on April 27 2018, when Infinity War finally arrives and whatever the other movie ends up being called is scheduled for April 26, 2019. Before then, we still have a number of Marvel adventures to see including Strange's introduction in a couple of months, a second Guardians and Thor: Ragnarok.