Overwatch Halloween Terror 2019 release date has not been revealed. The annual Halloween event for Overwatch typically releases around mid October, just in time for some celebration before Halloween.
Overwatch Halloween Terror 2019 Release Date
A recent Reddit post on the main Overwatch subreddit cited some leaked pictures that showed potential content that would be released during the Halloween Terror 2019 update. However, many users claim that the pictures are photoshopped or faked, and that much of the information is likely inaccurate.
An important thing to note though, is that Overwatch for the Nintendo Switch will be releasing on Oct. 15, 2019. This happens to coincide right with the middle of October. In an interview regarding Overwatch on the Nintendo Switch with Matthew Hawley, he explicitly stated that on the day that Overwatch goes live on the Switch "there's some other fun stuff happening on the Overwatch servers that day." This heavily implies that the Halloween Terror update will go live on Oct. 15.
Photo courtesy of Blizzard