Snyder says that, "I know for a fact that Frank [Miller] is writing right now." Like the original, Miller is first putting the story in graphic novel form before it makes it to a screenplay.
Apparently Miller is still "drawing away and seems to be knee-deep in it. I think he's going to head back to Greece again and do another reconnaissance."
As far as the style of the sequel, Synder says, "I think we would use the same technology... I don't want it to look too Star Wars-ian... Just from what [Miller] told me, it would be bigger as far as landscape and terrain. We're going to see Athens and the Aegean and other places. There would be an opportunity for bigger visions, though I'd hope for the same aesthetic. The tech we used for '300' was not a revolution. It's basically what the weatherman has. Look, instead of Accuweather it's Sparta... It's going to be the same way, but on crazier steroids."
Wow, we can already imagine the new 300 quotes we're going to be stuck hearing for years to come after this sequel.