According to the L.A. Times, a screenplay has been completed by Mark Protosevich (I am Legend, Poseidon) for a live-action adaptation of Thor and early details indicate that Matthew Vaughn (Layer Cake, Stardust) is being approached to direct the film.
Vaughn was originally tapped to direct X-Men: The Last Stand, but backed out to instead direct Stardust. Additionally, in the same article, the studio announced intentions to spin-off the Silver Surfer from the upcoming Fantastic Four sequel and pursue a darker course for that film series as they hope to attract an older demographic.
J. Michael Straczynski (Babylon 5) is currently crafting the screenplay. He has done prior work for the series as a writer on the comic book series, with the first issue of his “Silver Surfer: Requiem” series having just been published last month. Three more are in the works.
Source: L.A. Times