Peter Jackson has begun his 20 Questions for The Hobbit, just like he did for The Lord of the Rings, and the first question asked if we will get to see The White Council attacking Dol Guldur. Jackson, while not going into specifics, says that both the White Council and Dol Guldur will appear in the movies:
I’m not going to say just what and when, but I will confirm that both the White Council and Dol Guldur will feature in the movies. And not just in one scene either. Just how to visualise it has been a challenge, but fortunately Alan Lee and John Howe went crazy with ideas, and it should look pretty cool.
In Tolkien lore, Dol Guldur was where Sauron was hiding out in Mirkwood. Gandalf goes there, finds ThrÃ¡in (who gives him a map of the Lonely Mountain for Thorin), and then the White Council attacks; causing Sauron to flee to Mordor. If they show all of that in The Hobbit, it’d be pretty awesome.