Since Arkham City was released in 2011, Mark Hamill seemed to have ended his career as The Joker or that's what people thought. Over the last few years, rumors of The Killing Joke animated movie has been brought up which Mark himself said he was interested in. In 2012 Mark did an interview where he was asked about whether he give up the role and if he'd do another Arkham game "Never say never" was his reply.
Kevin Conroy and a lot of the fans have been instrumental in wanting Mark to come back as Joker. With Arkham Knight being the final game in the Arkham series, it couldn't be an Arkham game without an appearance from the Joker. Perhaps in a cameo/flashback or a return from the dead situation like in Batman Beyond.
Last time Mark spoke of Joker he admitted that he missed him very much and that he wouldn't rule out returning to voice him once more. Whatever the future brings's let's hope we hear that familiar once.
2015 is a big year for Mark Hamill. He will return as the Trickster in the Flash and of course as Luke Skywalker in the upcoming Star Wars movie. It wouldn't be a surprise if he does reprise his role as Mr J. His attitude towards working with Kevin Conroy has been highlighted and we can only imagine that we will hear that Joker voice one more time.
Would you like Mark Hamill to return as The Joker alongside Kevin Conroy once more?
Arkham City seemed to have ended Hamill's time as The Joker. The Joker dying due to the cure for his illness being smashed.