Waddle Dee/Bandana Dee
Popularity: Has some popularity in Japan. Not that much in the West.
Relevancy: He's one of the remaining plausible reps for Kirby, but in the end, he's a glorified grunt.
Design: They could work something with the spear, but he doesn't have the most potential out there (feels like he'd be somewhere between Kirby and Meta Knight)
Roster: The big three of Kirby are already represented, and there are other series waiting for their first reps or additional reps that should come first IMO. Putting in Waddle Dee would also most likely require changes to King Dedede's move set, unless he was made very visually distinctive from regular Waddle Dees (even so, it would seem weird).
Competition: Prince Fluff and Knuckle Joe have decent chances of taking a new Kirby slot as well without being as generic or requiring changes to Dedede. But I find a new Kirby slot highly unlikely in the first place. Sakurai doesn't want to overly promote his own series, he already has the major players from Kirby and if he puts in Palutena, he'd already be adding one of "his" characters. He might also be a little wary of showing favoritism because of how overpowered he made Meta Knight.
Waddle Dee chances: 2%
New Kirby rep is quite unlikely, he's not the most interesting character, he's part of Dedede's move set, and other Kirby reps could get in instead even if a new Kirby rep happened.
Waddle Dee/Bandana Dee: 23%
(50% is indifference, 0% is hate) Kirby is complete as far as I'm concerned, would prefer most potential characters over him, unless we had a huge roster.
Jigglypuff prediction: 94%
Some on GameFAQs are gonna hate, but I don't think most people are expecting her to be cut, even if she's in more danger as a more ancillary character.
Nominations:
5x Toad