Oh. I was actually still holding out for some kind of duet between John and Katy to be honest.
Seems a bit random for her to make a diss track about him, they didn't seem to end badly and they didn't seem to even be dating *that* seriously... Meh, I'm sure she'll have her reasons if it's true. I can't imagine a Russell diss track either though, that seems more likely to be a ballad about losing someone.