[Update: WB Montreal has teased the game yet again! Check it out here]
Amazon had recently posted placeholder listings for a new game by WB Montreal for the PC, Xbox One and PS4 though they were soon taken down after. The sudden appearance of these listings, however, seems to most likely hint at the fact that the studio will soon be revealing their next title.

WB Montreal previously worked on Batman Arkham Origins, a prequel to Rocksteady’s Arkham Asylum.
Whatever the truth is doesn’t matter as, if the listings are any indication, it should be confirmed soon enough, possibly at Gamescom which begins just later this month.