The answer appears to have been revealed: it’s another duet, and one of the artists involved is a cast member.
The other is someone Zayn actually knows very well.
According to posts on Instagram and Twitter, it’ll be Liam Payne and Rita Ora who lead the charge; the latter, of course, having a small role in the movie too.
Payne and Ora seemed to drop the news on their profile, posting a photo of the two artists together along with the caption: “#FiftyShadesFreed.”
The official Fifty Shades account shared both artists’ pictures.
The theme song to a movie in the franchise is big business: Love Me Like You Do, recorded by Goulding in 2015, topped charts around the world and was the fourth biggest single in the UK of that year. It also topped a billion views on VEVO.
Swift and Zayn, meanwhile, released I Don’t Wanna Live Forever last year and also had global success; hitting No2 in the US and No5 in the UK.
Fifty Shades Freed stars Dakota Johnson and Jamie Dornan as Christian Grey, for the third and final time.
Rumours that they could reprise the roles once more for an adaptation of new book Grey – which retells the first story through the title character’s perspective – were dampened when the publication failed to sell the same huge number of copies.
It’s still a hugely successful franchise, however, despite poor critics’ reviews.
Fifty Shades Freed is out on February 9, 2018.