Lets start with The Man first, we know her team suddenly pulled it from radio. Isn't that suspicious? the song was literally having good updates, but if she was to release a new single then it will make sense.
Lover era is Taylor's first era with Republic Records. Almost all artists under the label release standalone SINGLES after their album releases (Ariana, Drake, Post, The Weeknd, Nicki), if Taylor does that then it means that she will release a new single soon.
An evidence of her recording something new is that we know she went into the studio in December with Jack Antonoff and Laura Sisk and its NOT for Only The Young or Christmas Tree Farm.
Y'all probably don't know but Post Malone is a friend of Taylor (they praised each others music a LOT) and he is teasing "big news", if you think about it The Man was just dropped and can most definitely mean an announcement for their collab.