The real question is will Ant-Man be a regular on Avengers Assemble or just a guest character. I'm hoping he becomes the eighth official member of the team. After all, there should be more members for Season 2, same way they added more characters in Justice League as episodes progressed.
Are they getting a second season? If so then he probably will as they should want him to get his character more presence before the movie. I am surprised Guardians of the Galaxy haven't made a appearance but maybe that is something slated for a second season.