The CW's DC TV show universe - also referred to as the Arrowverse and/or Flarrowverse for Arrow and The Flash - has expanded a good deal, over the course of the past year. Not only did an Arrow/Flash spinoff in the form of DC's Legends of Tomorrow debut, but a crossover between The Flash and former CBS TV show Supergirl established the latter as being part of The CW/DC "multi-verse." Now that Supergirl has set up camp at The CW for its second season, crossovers between all-four CW DC TV series are actively being planned too.
However, lest we forget, the most recent season of Arrow (season 4) also introduced Matt Ryan's John Constantine to the Arrowverse, following the cancellation of the Ryan-headlined Constantine TV show on NBC. That leaves the door open for future appearances by the supernatural-savvy detective on any of The CW's four DC Comics-based TV series - even if, currently, there are no concrete plans for the "Hellblazer" to again cross paths with the likes of Oliver Queen and his allies, anytime soon.
Arrowverse co-creator and co-showrunner Greg Berlanti had the following to say about the future of Ryan's John Constantine, when asked during The CW's panel at the Television Critics Association press tour (via IGN):
"We haven't had any conversations with [The CW] about Constantine. [John] Constantine exists in a certain place in the DC world and universe [and] they're kind of internally examining what they want to do with that character next."
Berlanti, lest anyone get the wrong impression, went on to praise Ryan's performance as the witty (and damaged) John Constantine as being "terrific" and clarified that he and his fellow Arrowverse producers simply haven't made any firm plans involving the character - yet. It's not surprising that Constantine has been put on the back-burner though, what with everything else that will be happening in the Arrowverse over the upcoming season. That includes: a version of the Flashpoint storyline during The Flash season 3; both the Justice Society of America and The Legion of Doom appearing on Legends of Tomorrow season 2; and Arrow getting back to its street-level crime-fighter roots in season 5, after its more supernatural-heavy season 4 (a setup that better lent itself to Constantine appearing on the show).
However, Legends executive producer Phil Klemmer has told Zap2it that “If this show goes as many seasons as I hope it does, it would be a crime for [Constantine] not to appear in our universe.” Indeed, as magic is going to continue being a key part of the Arrowverse in the future (especially with the Arrow season 4 villain Damien Darhk (Neal McDonagh) serving as a member of the Legion of Doom), there ought to be opportunities for John Constantine to return to the fold down the line.
The Flash season 3 will premiere Tuesday October 4th at 8pm on The CW, Arrow season 5 will premiere in the same timeslot on Wednesday October 5th, Supergirl season 2 on Monday October 10th, and Legends of Tomorrow season 2 on Thursday October 13th. We'll bring you more information about Constantine as it becomes available.