Honestly, when it comes to third party DLC at this point.
I strongly believe Ryu is the only one we're getting.
Because the entire contractual negotions with a whole company (like Konami or Square-Enix) for a DLC character who likely won't get extra trophies outside of the 3 for the fighter, an assist trophy, and maybe not even a stage seems like something that won't be done.
The only "hope" for 3rd Party DLC would be from situations like the indie companies who appear to be willing to bend over backwards to make things as easy and seemless as possible for a Smashification. (With the issue being how much the All-Star Icon 3rd Party point has been stressed obviously excluding almost any option)
Of these, Shantae is the only one I would say is able to throw around enough weight to seem plausible, having 3 titles with 4th on the way who have at least started as Nintendo Exclusive, and is from a company that shoves any passion project onto Nintendo Consoles (Every Mighty ___ ___ title, Shantae: Pirate's Curse, Risky's Revenge, and I believe 1/2 Genie Hero) and a very Smash-happy feel to her games, potential moves, and design.
And because Mr. Bozon would be in HUUUUGE legal threat if he was saying anything about Shantae being ready for Smash if she was planned pre-ballot, her only hope is to pull a major impact in the ballot, which is truly debatable when you have some significant 1st Party characters storming the scene and we'll be seeing less than a half dozen from the ballot assuredly imo.