we do not know the exact details of the movie but previously we hve heard that it would involve Monsters Inc university.
According to the disney blog the movie does have a University bent to it, but instead of Mike Wazowski (Billy Crystal) and James P. Sullivan (John Goodman) going back to school as professors (as some of the past reports speculated) this movie will be an origins tale. Crystal and Goodman are coming back as college years Sully and Mike. "The sequel will tell the story of Mike and Sully's first meeting at school. They couldn't stand each other, but they overcame their differences to become friends."