Thanks to hot screenwriter du jour, Laeta Kalogridis (she penned Marty Scorsese's "Shutter Island"). While she's not directly credited on the "Avatar" screenplay, it's no secret that she was a big story sounding board for Cameron, who worked with her previously for the script to his still-unproduced and long-gestating projects "Battle Angel" and "The Dive" (her work on "Avatar" earned her an executive-producer credit).
Now, she's been tapped to give the "Fantastic Voyage" script an overhaul according to THR. Evidently several scribes have taken a stab at the Fox project, including Shane Salerno ("Armageddon," "Alien Vs. Predator") and married duo Cormac and Marianne Wibberley ("National Treasure: Book of Secrets"), but neither of those passes were evidently strong enough to keep Greengrass onboard who has evidently moved on to an adaptation of "Treasure Island" (whoda thunk, gotta say that seems like a weird one for him).
No new director has been found, and we assume they won't look until Kalogridis' draft is ready. The in-demand screenwriter has also worked on "Ghost in the Shell" for DreamWorks, wrote an early draft of "X-Men," rewrote a "Wonder Woman" script for WB, was involved in a "Lone Ranger" remake at Columbia, and has screenwriting credits on "Alexander" and "Lara Croft: Tomb Raider" among several other gigs.