Abba, the legendary Swedish pop group that sold more singles than any other band, say they might be coming back. But have they ever left? Abba never officially broke up, though they haven’t had a new album since 1982. Abba’s songs have continued to be covered and sampled. Abba’s hits were turned into a Broadway show and then a movie called “Mama Mia.”

And now Abba is mulling a possible “Waterloo” reunion.

Singer Agnetha Faltskog revealed that the Legendary Swedish pop group ABBA may reunite next year to celebrate the 40th anniversary of their signature hit “Waterloo.” Abba’s song won the Eurovision Song Contest, England, in April 1974 and the band was thrust onto the world stage. Abba quickly became Sweden's biggest-ever pop act and ultimately one of the most successful pop groups in history. Abba sold over 380 million records worldwide.

Agnetha Faltskog, who is 63 now, told the German weekly Welt am Sonntag "Of course it's something we're thinking about. There seem to be plans to do something to mark this anniversary in some way. But I can't say at this point what will come of them."

Welt am Sonntag, Faltskog just put out a new solo album. She isn’t thinking too much about an Abba reunion, she says "That eats up too much energy. Don't just think about it, just do it. We're all getting older. I can't imagine going onto the stage on walking sticks."

ABBA was formed in 1972. Agnetha Faltskog met her future husband, the guitarist and songwriter Bjorn Ulvaeus and they teamed with Benny Andersson and Anni-Frid Lyngstad, who were also married for a while, to create radio friendly hits. Both couples were later divorced but that won’t stop them from reuniting.

Abba went on to record such as "Mamma Mia", "Dancing Queen" and "Super Trouper".

Abba’s last album "The Visitors" came out in 1982.

Since Abba stopped recording, Faltskog and Lyngstad each tried to go it solo. Andersson and Ulvaeus wrote the musical "Chess," which became a hit. They then turned Abba’s biggest hits into the smash musical "Mamma Mia."

The four members of Abba got together for the Swedish premiere of the film version of “Mamma Mia” that starred Meryl Streep and Pierce Brosnan in July 2008. They hadn’t been seen together in public since 1986.

But at the time, Ulvaeus and Andersson said there was "simply no motivation to regroup. We would like people to remember us as we were, young, exuberant and full of ambition."

On May 7, an ABBA museum opened in Stockholm.