Reports have been circling that filming for The Hobbit will be pushed from the original date of March 2010 to mid-summer 2010. German website caught up with writer/producer Peter Jackson, who confirmed that The Hobbit and The Hobbit Sequel will indeed start filming mid-summer 2010. translated some of the quotes:

We're currently working on the second script which we hope to have completed by the end of this year or beginning of next. When the scripts are completed, we can begin with the exact calculation of the necessary budget. We hope to start filming in the middle of next year. However, we've received no green light from the studio yet.
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Jackson did not mention whether this will affect the expected release dates of December 2011 and 2012.