The Warner Bros Studio in Hollywood announced that the Horror Made Here: A Festival of Frights event would not be produced for the 2019 haunt season. It appears that something is being added to the studio tour. Those details will be revealed later this year.
The Warner Brothers Studio Tours (Studio Tour, Classics Tour, Deluxe Tour, and other events) are still operating as usual. It is just the signature Halloween event that will be dark this fall.
You can stay up-to-date about the Warner Bros Studio Tour: Hollywood at the official website here - https://www.wbstudiotour.com/