So, in other words, please wait to spread these details around to other forums/sites/blogs until there is a formal announcement or until some reputable film blog posts it as a scoop... which I'm guessing might happen soon if it all works out.
From Production Weekly (dated 10/07/10, issue 733):
*In case it is confusing, 04/08/10 is the date when the Production Weekly entry for the film was last updated.
There was some random who posted a thread today about Akira on Zac's imdb board stating it was a rumor that WB wanted him for Tetsuo in Akira. I'm not sure if they saw this same info or just saw it on his Baseline account (where we first saw it a year ago). The timing makes me think they saw it in Production Weekly, which means they don't really know which character they want him for.
TBH Zac for Tetsuo doesn't totally make sense to me. I definitely picture him more as Kaneda who is a charming and likeable rapscallion, even if he's a bit full of himself. Tetsuo is the crazy one who suffers from quite the inferiority complex. I know that as an actor, Zac should be able to do a variety of roles but it seems, in this case, wise to work with your natural energies, especially since Kaneda, as the hero, is just plain cooler (though who isn't envious of Tetsuo's whack mutated arm).
Either way it is exciting cause Zac has expressed publicly and privately that he is very interested in an Akira live-action adaptation. Hopefully it does come together for him and further hopefully the script and execution is awesome.