Here's a final draft of a 'DLC likelihood' tier list. Considered the input on the list yesterday.
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List assumptions (i.e. not necessarily true):
- Ice Climbers, the unaltered veteran character, are a technical impossibility.
- Snake complications are insurmountable.
- There exists the possibility of character DLC unrelated to the fighter ballot.
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S) A relevant veteran who places well in ballot polls.
A) King K. Rool historically #1 or #2 most requested newcomer behind Ridley. Inkling places well in ballot polls, is a popular new IP, and tbh if not in smash 4 will be in smash 5.
B) Isaac historically top 5 most requested newcomer. Isaac holds the same character potential as K. Rool, however the King seems to place slightly higher in polls. Bandana Dee garners a good amount of support internationally.
C) Dixie Kong is another top 5 most requested character historically but is typically next in line to K. Rool. Krystal is in the Dixie Kong boat, behind Wolf. Krystal could be in over Wolf, but it'd be an upset.
D) Shovel Knight or Shantae the obligatory indie characters. Cult popularity in some regions, indifference in others. Some don't like the idea of indie reps 'taking first party spots'. Chorus Men don't hold presence in ballot polls but were rumored to be in early stages of Smash 4 development. Paper Mario has many supporters and character potential, however some people don't like the idea of a third Mario. Impa gained an edge on Groose as the Zelda newcomer with the release of Hyrule Warriors, but still doesn't hold much star power. Nintendo's been pushing Chibi-Robo with an amiibo and advertisement, but would be an upset to other characters. Wonder Red had strong support at the release of Wonderful 101, but died down in popularity.
E) Third party tier. While not lacking support, Nintendo has less incentive to include these characters. Consider them Nintendo's stepchildren.