So you mean like, the two free slots are extra characters not part season pass and maybe the center slot is a DLC slot for the rest of the season pass or something? That would be amazing but wouldn't happen in a million years (though there is still this question of where the third DLC character goes).
It would be nice though to think that if the game is selling well, they might think "y'know what? we couldn't deliver the roster the fans wanted, but we got good sales so here, have some free characters to flesh it out". Again, wouldn't happen in a million years but it's a nice thought. I know if I was a developer that's something I would do but then I'm too nice for my own good.
I really hope the announcement is one or more of the DLC characters. Gotta be right? Unless what they think is a big announcement and what WE think is a big announcement don't align, which wouldn't surprise me...