At the time, there wasn’t much to back up the report, other than it sounds like a reasonable possibility. There are tons of movies based on comic books and tons of movies based on video games, so the next natural progression might be to base a movie on a comic book video game.
Now, Fusible.com has uncovered a list of domain names supposedly registered by Warner Bros. which might give some support to the Batman Arkham Asylum movie theory. A number of Arkham related domain names have been registered through the domain registrar that has been previously used by Warner Bros.
The domains registered include arkhamuniverse.com (Arkham Universe) batmanarkahmuniverse.com (Batman Arkham Universe) batmanarkhamarises.com (Batman Arkham Arises) batmanarkhambegins.com (Batman Arkham Begins) batmanarkhamdarkknight.com (Batman Arkham Dark Knight) batmanarkhamknight.com (Batman Arkham Knight) batmanarkhamlegend.com (Batman Arkham Legend) batmanarkhamlegends.com (Batman Arkham Legends) batmanarkhamnight.com (Batman Arkham Night) batmanarkhamorigins.com (Batman Arkham Origins) batmanarkhamstories.com (Batman Arkham Stories) darkknightarkham.com (Dark Knight Arkham) dcarkhamuniverse.com (DC Arkham Universe) dcarkhamverse.com (DC Arkhamverse) thearkhamuniverse.com (The Arkham Universe)
Of course, it could be that Warner Bros. is just registering the domain names for another upcoming Batman video game, which they have done in the past. In fact, several of the domain names sound more like something that would be used for an online video game rather than a movie. However, a couple of them do have that movie title ring.