It's not C21 to have a film based on the battle of Thermopylae.
It's not even C21 to have a Frank Miller comic book based on the battle of Thermopylae.
But it's a little furture-shock-wierd to have a film based on a comic book based on the battle of Thermopylae. 
(It must be the same future where Dave Cockrum, best known for
 Due to the wierdness of Hollywood (and as this post notes that wierdness is understandable and, indeed, sometimes a good thing) the time between wrapping a film and it's release is a good time for those involved to pitch their next projects(s). The director, has Zack Snyder attached himself to Watchmen, which is a film that really should have been made in the 20th Century.