I just heard in a local newspaper, the manuscript for The Hobbit will be done in a few weeks! That means, when the casting is fixed, they can start filming^^

I expect that they will start filming next summer or spring. With a late 2011 projected release date, they cannot begin filming too soon. Jackson said at Comic-Con “We’re about three weeks away from turning over the first draft of the script to the studio.” http://www.empireonline.com/features/co ... asp?id=597

So they're three weeks away from the first draft being submitted. Then they need to make casting decisions. Then they need to actually refine the script and get it in filmable condition. Then they need to cast the smaller parts of the film. And there's a lot of other pre-production stuff (including concept art, storyboards, CGI tests, etc.) that will take a few months.