The legendary Swedish pop group ABBA is mulling a possible reunion next year, singer Agnetha Faltskog said in a German newspaper interview Sunday. Next year marks the 40th anniversary of the band's first hit "Waterloo", which won them the Eurovision song contest and catapulted them to fame. ABBA subsequently became one of the world's best-selling pop bands with a string of number one hits such as "Mamma Mia", "Dancing Queen" and "Super Trouper