It'd be best to wait & see if the next DLC will be free for two weeks so that you can see if that's a thing they're doing for every DLC.
As of now, it's just them + the stage. No one knows unless they were asked, which they haven't been asked yet.
I think the only reason Kat and Emmett are free for 2 weeks is because they were meant to be in the initial roster.
I like the idea of paying for future DLC. I'd like to have a match where every player isn't the one I main, ya know?
That's not how it is.
They weren't meant to be.