The Swedish band launched a new website on Thursday morning titled "Abba Voyage", asking fans to register interest in a new project.
It is expected to be a long-gestating "hologram tour" that Abba initially announced in 2016.
The band are also expected to release five new songs to accompany the show.
The quartet - Agnetha Faltskog, Anna-Frid Lyngstad, Bjorn Ulvaeus and Benny Andersson - returned to the studio in 2018, promising two new songs later that year.
Those tracks, I Still Have Faith In You and Don't Shut Me Down, have been repeatedly delayed - and the band are now planning to release five tracks to thank fans for their patience.
Earlier this year, Ulvaeus confirmed the music would "definitely" come out this year.
"It's not a case any more of it might happen, it will happen," he told The Herald Sun.
The Abba Voyage website was launched on Thursday morning, featuring a cryptic image of four glowing planets, accompanied by the date 2 September.
According to The Sun, the show will involve "Abba-tars" of the stars performing hits like Waterloo, Dancing Queen and Mamma Mia.
It said the holograms will be beamed onstage in a purpose-built east London theatre, where fans will also be able to see a documentary-style film on the band's comeback.
Speaking to the BBC during the early stages of the show's production, Ulvaeus said the idea had been presented to the band by Spice Girls manager Simon Fuller.
"He came to Stockholm and he presented this idea to us that we could make identical digital copies of ourselves of a certain age and that those copies could then go on tour and they could sing our songs, you know, and lip sync. I've seen this project half-way through and it's already mind-boggling."
Filming for the project reportedly took place at London's Ealing Studios last year.