The film was inspired by the wildly popular ABBA jukebox stage musical of the same name co-starring Meryl Streep, Colin Firth and Pierce Brosnan. The film earned $500 million at the global box office.
"I've been talking to some insiders and it's not something that they haven't been working on. I don't actually know anything other than that," Seyfried told the BBC's Newsbeat program. "I know it's still going to be ABBA music, because what else would it be? Come on, I wouldn't do 'Mamma Mia 2' without (ABBA singer-songwriters) Benny (Andersson) and Bjorn (Ulvaeus.) I will do it. And I know Meryl's game as well, so bring it on. It will be so cool."
Ulvaeus said last April he had no interest in helping out on a sequel, however, because he is busy with other projects.