Constantine will be returning to investigate the supernatural and defeat the sources of darkness as it's been announced that J.J. Abrams' Bad Robot production company is developing a "darker reboot" of the DC Comics character for HBO Max. The series will be penned by Guy Bolton, who has already written the pilot script and will be opening up a writers' room next month.
Keanu Reeves played the role of John Constantine in the 2005 movie, with Matt Ryan taking on the mantle of the occult investigator in NBC's short-lived series before making appearances on Arrow and Legends of Tomorrow, thereby bringing the character into the Arrowverse. Unlike the last two incarnations of John Constantine, it's been said that this version of the character will be played by a diverse lead. It's also been said that this new series will follow a younger version of John Constantine and will focus more on the horror elements of the comics rather than the religious ones.
J.J. Abrams made a multi-million dollar deal with WarnerMedia in 2019 to develop all types of content for the company, and one of those projects was revealed to be a Justice League Dark series. In the comics, one of the characters who make up Justice League Dark is John Constantine, so it's possible that we might see some of the other characters on the team receiving their own shows before joining forces for a team-up series. That's just speculation on my part, but stranger things have certainly happened.