Variety broke the news that the films coming out in 2018 and 2019 under the Avengers banner will not share the same titles with a Part One and Part Two as subtitles. The first, to debut in May of 2018, will be titled Avengers Infinity War. The second is now untitled (although still an Avengers movie).
The news has everyone talking and speculating. Will the film premiering in 2019 be connected to Infinity War? Will it be entirely separate? It’s very unknown at this point.
In the comics Infinity War was one of three major storylines that struck the Marvel Comics Universe at different times. The others were Infinity Gauntlet and Infinity Crusade. It’s possible that the 2019 film will adapt these other stories while War will be adapted from one of the others. This is just my speculation. The second film could be entirely different.
The Russo brothers, who have helmed the last two Captain America films, are still on board for the two upcoming Avengers films.