The 'Let Me Entertain You' hitmaker took to social media to share a black and white photo of himself back in the studio, leading fans to speculate he might be working on a Christmas album.
Robbie didn't give the game away, leaving the caption blank but a stamp on the photo says it was taken on May 28, 2019.
Meanwhile, Robbie's collaborator Guy Chambers recently revealed his friend's approach to creating new music is often quite spontaneous, and he has to make sure he's always recording just in case the singer does something "really very strong".
He said: "[Robbie] gets quite a buzz from a track already in progress. He likes a certain amount of music to ... So what we tend to do when he walks through the room is we immediately give him a mic, a handheld mic, and he immediately starts singing, if he likes the track. We record everything he does, because sometimes his first thoughts are really very strong, and I'm sort of playing along at the same time trying to interact with him. I like jamming with people when I'm writing. I like playing at the same time, I like getting involved, and not just watching it. I like ... I suppose directing it in a way, and that's what it's like with Rob."
Earlier this year, it was claimed that Robbie wants to make another swing album after being inspired by his Las Vegas residency.
An insider said at the time: "Robbie is a huge fan of swing and believes his performing style of singing and joking with the audience has a direct link with greats like Sinatra and Martin.
"Getting on stage in Vegas, where those guys were kings, to sing those tracks again has given him the impetus to make another swing record. He's starting to list the songs he wants."