Avengers: Infinity War is no longer planned as a two-part film, according to Variety.  Disney still plans to release Avengers:  Infinity War on May 4, 2018, as originally announced (see "Geek Movie News Round-Up" and "Best in Shows: Q2 2018").  But the second Avengers film directed by the Russo brothers, still scheduled for May 3, 2019, is now just an "Untitled Avengers" film.

Whether this really means that there’s been a significant change in the planned storylines is unclear; it may just be a repackaging of the two films in a way that the studio believes will be beneficial to receipts.

Both films are being written by Christopher Markus and Stephen McFeely (see "Geek Movie News Round-Up May 2015").