Before I say this, this is my interpretation of what's to come, so if I offend anyone with this, I'm sorry. I can always be wrong. Please don't start another flame war over it.
With this new development, I'm very confident we can still get a DK newcomer. However, I don't think we can get K. Rool/an original Dixie moveset alongside Ridley. With the way the way the CSS in the leak is ordered, that is, series with 2 or more characters are put in chronological order of their orignal release (Mario, DK, Zelda, Metroid, Kid Icarus, Fire Emblem, Kirby, Star Fox, Pokemon), the only way that can happen would be for the rows to extend from nine to eleven, which I don't think is happening. I can see the roster expanding to ten rows, but not eleven.
With this in mind, I think there are still a few possible scenarios on how this can go down, not counting potential DLC down the road:
1. K. Rool and clone* Dixie (on the roster, Dixie goes in between Dr. Mario and Dark Pit; this is probably the solution that will appease most DK fans)
2. Ridley and clone* Dixie
3. Original Dixie in the DK section and neither K. Rool nor Ridley (very unlikely IMO, as much as I want a completely original Dixie)
4. No DK newcomer (I'm hopeful this isn't the case)
*: the definition of "clone" in this case does not necessarily mean a 1-to-1 clone like Lucina. I'm assuming that Dr. Mario will probably have the Mario Tornado instead of the FLUDD, which would leave room for these clone characters to have different specials. Dixie could still have moves like her hair spin as an Up-Special, but I think she would have a lot of moves taken from Diddy if she is put into this section (which I would be fine with; Diddy already has a solid moveset).