According to IMDB (hence the bit of salt I mentioned), director Edgar Wright (Scott Pilgrim vs. the World) says that both Hank Pym and Scott Lang will appear in the film. He also states that Ant-Man will appear in the Avengers film. The script is currently in the second stage of writing and it will be Wright's next project once Scott Pilgrim is complete. The site also states that the film will not be an animated film in conjunction with Pixar as once speculated.
ecksmanfan: Two things: 1) I am sorry if this is old news, just wanted to get the info out there. 2) Being that this info is from IMDB, it is hard to take it seriously. I'd like to see him as a part of the Avengers film, but I'd be surprised if it was a major part. Time will tell.