Unlike the first two phases, the Marvel Cinematic Universe Phase Three will consist of more than a dozen movies. Phase One and Phase Two featured six movies each - five standalone movies and one Avengers movie. In Phase Three, there will be two Avengers movies which were announced to be titled Avengers: Infinity War – Part 1 and Part 2.
However, according to The Hollywood Reporter, Walt Disney Studios has officially updated the titles of both movies. The nineteenth MCU installment, which was previously titled as Avengers: Infinity War - Part 1, will simply be termed as Avengers: Infinity War from now on.
The twenty-second one will no longer be called Avengers: Infinity War - Part 2. They have yet to confirm a title for the movie but for the time being, it will be referred to as an untitled Avengers movie.
The release dates of both movies remain intact – Avengers: Infinity War will hit the theaters on May 4, 2018 while the untitled Avengers sequel will release on May 3, 2019.

The title changes for the upcoming Avengers movies don't come as a surprise, considering the fact that the Russo Brothers had confirmed that they would change the titles a few months ago.
According to the directors, despite being filmed simultaneously, these are "two very different movies". They claimed that labeling the movies as Avengers: Infinity War – Part 1 and Part 2 is "misleading".
In recent years, studios have come to realize that splitting a movie into two parts doesn't please the audience at all. Hunger Games: Mockingjay - Part 1 and Part 2 are the best examples. Part 2 was the lowest-grossing installment in the franchise.
And Marvel Studios isn't the first studio to change the titles of movies originally titled as Part 1 and Part 2. Lionsgate did the same with The Divergent Series: Allegiant Part 1 and Part 2. They retitled the movies as Allegiant and Ascendant.