That's what says Jim Sullos anyway, president of ERB inc, in the l'article linked below. The recent financial failure of John Carter seems to paralyze movie producers, even if they still show interest in the property. "There may be more interest in a television series than a sequel to the film." Nothing official yet of course, The rights for a live-action or animated adaptation are still available.

http://www.sfvbj.com/news/2015/jul/24/preview-mars-or-bust/

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