Shane Black (Kiss Kiss Bang Bang, Lethal Weapon) the director and co-writer of Iron Man 3 was speaking at the Long Beach Comic-Con (via ComicBookResources). He gave up brief details on the third installment which included one villain that won't be included along with who will be returning.
Mandarin is a villain Black doesn't want to see included as he's "a racist caricature". Which might be a shock to Jon Faverau who originally wanted to use him. Jon Favreau, Gwyneth Paltrow and Don Cheadle are expected to reprise their supporting roles. He also stated the film won't be focused on The Avengers or Easter eggs.