I appreciate Dixie being the first female that comes to mind for you (and I would really want her to be the one in this situation), but I highly doubt Dixie would randomly be thrown into next year's DLC. The only Nintendo characters I see as a possibility are Astral Chain's Akira Howard or a character from Fire Emblem Three Houses (both titles still never received a spirit event in Ultimate, which is very peculiar).
In general, I think if a female newcomer is included next year (assuming Fighters Pass Fighter #5 is not one or does not have a female alt), she most likely will be Arle or Reimu. Both would be a Japanese equivalent to Doom Slayer, a character who is very popular in a particular region, but obscure in another. I think Doom Slayer is coming, and I do see them trying to balance his inclusion with a character with high particular Japanese appeal, and I think both of those character fit that. Even if a Nintendo character is chosen for the female rep both of the most likely Nintendo character examples I listed (Astral Chain and Fire Emblem Three Houses) have female choices within them (Akira Howard has a male and female version, and Byleth does as well, as well as Edelgard being exclusively female).
I would really love for it to somehow be Dixie Kong as the female newcomer Nintendo hopes to include, but I don't see them seeing Dixie as "female" because she is not a human/mostly human woman, which is what most of the Smash fanbase here means when they say that they want, "more female newcomers", which is really a shame because she is probably the most important female Nintendo not yet on the roster, and arguably the most important gaming one (though Arle outclasses her on the Japanese side of things).
I want to be proven wrong on this, but I doubt Dixie would get picked for explicitly filling out a female DLC character slot. Again, I appreciate Dixie Kong being what comes to mind when you thought about a female newcomer being DLC (she is truly among the few Nintendo icons left not part of Ultimate's legendary roster), and that myself was tagged in relation to this.
For others reading this message, I am sure many of you are either unfamiliar or barely familiar with Dixie Kong, or might even just simply think of her as "that girl Kong". Dixie Kong is far more than that. She is a legendary heroine and was absolutely historic for the time she made her debut. I wrote an essay a few months ago explaining just what makes Dixie Kong
special and why I believe in many way she is the ultimate
heroine.
Here is a link to the work:
https://smashboards.com/threads/dix...eators-of-dkc-on-youtube.446464/post-23549985
I am not sure if what I wrote will convince any of you or change minds, but it might offer a perspective about why she is so endearing to her fans. Please give it a look when or if you have the chance.