Breaking Dawn Returns to Vancouver on January 11, 2011

According to Production Week

Filming (in Baton Rouge and Vancouver) is scheduled from November 1, 2010 - March 15, 2011.

via lion_lamb via RPLife

ETA: Some of you are having questions about filming in Louisiana. Louisiana has one of the best film tax rebates in the country. For a certain amount of money that Summit spends in the state, the state will give 30% of that money back to Summit. Summit can then use that money to help another aspect of production (i.e. more money for special effects, etc.)
Louisiana has several film studios and sound stages for film use, so the fact that they are filming in Louisiana is more than likely a product of how much money they can save by filming there, and not actually Louisiana's "look," although the state has been used to look like several other filming locations around the world. Click HERE for a list of productions, by year, that were filmed in Louisiana.