Isaac * - Golden Sun representation has been lacking since Pre-Brawl, and the upgrade to AT was a start, but this time around its more commonly to think that Isaac would receave a Playable Status, and if there are more characters to be revealed, I think he has a shot this way. So far he has survived the AT's Slaughter and the PotD's.
King K. Rool * - When it comes to most talked about villains for Smash K. Rool scores high on most lists. And being one of the most wanted characters, I don't see why he should be left out. DK needs their villain, and K. Rool is a character I believe is one of the last to unlock, which is why I think he might be in, just no unlocked as of the time they made the screenshot leak. If I'm wrong, I think he is a good candidate on the DLC list.
Ridley * - The only thing bigger than Ridley himself is his fanbase, and that has helped a lot of characters making it into the Smash franchise. Sakurai once stated it was too hard to make him in. But that was similar to what he said about Villager, but look at him now, pluss all the trolling of Ridley must mean something?! I think he has shot of being in. But most likley he is in from the start or I see it hard why Sakurai would troll him already... If not he is a stage hazard working the same way as Toon Link but not in the launch roster but a DLC for Ultimate Trolling by Sakurai?! ~
Ice Climbers * - It's hard to believe they are being cut, even due to what they said about their troubles. But then again rumours has it that they are planned as DLC. But what if their difficulities are still being worked on/tweaked so they have yet to be added to the primary game? Still time for debugging and adding you know.
Lucas * - Even tho, he is a clone, so is Lucina, Ganondorf, Dr. Mario, Toon Link, Falco and Dark Pit, so it would be sad to just leave Lucas out of the game, but have him as a DLC makes time for the developers to make him even more unique from Ness, and that could be a good thing for Lucas, so I feel it is somewhat right to add him as a DLC:
Wolf * - I remember everyone wanted to see Wolf make it in to the series, and when he did in Brawl, people started to shut up about Wolf. But even tho he was a total clone sort of settlement, I still think Wolf should come back, for his important role as a villain in the franchise. But as with Lucas it could give them more time to make Wolf more unique from Fox, and that is something I'd love.
Snake * - Snake never really fit in to the style, so it makes sense to not have him in. But then again I don't see it 100% likley that they will kick him out. His fighting style is very unique in the series, and that is a great thing that I think makes him still having a shot to be playable. But with 2 NEW 3rd Party characters, I believe he should be the DLC representive 3rd Party.
Squirtle - Even tho Pokémon Trainer is gone, and Charizard is a stand alone character, I still don't see a big reason to include Squirtle or Ivysaur, but both of them brings unique moveset to the table, which would be sad if they dissapeared like that. So they fit the bill's as DLC characters, so like this I would not mind at all.
Ivysaur - See Squrrtle ~
Lip - Even tho there might not be a lot of people who know who Lip is. We still got her stick as a weapon, and for those who knows her I can say that so does Masahiro Sakurai and he also said that he think her games are masterpieces. So it could give him a reason enough to include him as a DLC surprise without desturb the launch roster with a JAPAN Exclusive like Roy and Marth at the Melee times.
Dixie Kong * - Fight for the 3rd DK spot either goes to K.Rool or Dixie Kong, both strong competitors. But it seems like Nintendo is more in favor of having the third Kong as a playable in more stuff than the big ol'croc. But nothing is said yet. AND with the DLC's going on, there is a possible chance of both of them getting the playable status. But nothing is set in stone yet.
Krystal - Another character a lot of people wants to see, even tho most of her fans was on top around pre-Brawl. She still have support, and the most likley would be DLC status. In my opinion, the only Star Fox character that has same potential of different moveset is Slippy Toad, but the most likley would be Krystal.
Roy - No one knows if Roy actually will return for the 4th Installment. One things for sure, it will not be by the launch roster, so only chance homeboy Roy got is the DLC status. It only depends on how desireable Sakurai look at him at this time.
Mewtwo * - Not only relevent, but also incredibly populare. And with the leaks going on he is also stamped as a questionmark, so either he is in by launch or he is directly added as a DLC status character. I just hope he won't have that bad way to unlock him....
Toon Zelda or Impa - Toon Link returned, and the rumours that Toon Zelda was going to make it in to Brawl, makes me thing that she might have a shot as a DLC character, the other character I believe got a shot is Impa, which will most likley become a Sheik clone as Toon Zelda would be for Zelda.
Black Shadow - As a faithful Smasher, Falcon has fought alone for the F-Zero franchise, only briefly see his old rival Goroh on the field while he is summoned. But F-Zero should get 1 more character, and that should be Black Shadow. He has a lot of potential, and a semi clone type of character is also possible to pull on him, making him a top candidate for DLC.
Wonder Red - I think there is a possible chance, but I don't have much to speak about as of now.
Chibi-Robo - I would love to see Chibi-Robo make it in. He has a huge potential, and its a bit sad to think he is not in already and it would be a waste of oppertunity to see him not playable. If not, then maybe he appears as a Assist Trophy, but then I hope Doshin The Giant also gets AT Status, but if not then I hope for a DLC.
Bandana Dee - Another somewhat popular character I can see get a DLC Playable Status.
Professor Layton - Remeber the tweets back in the day, where he stated he fought a Blue Robot and a Boxer? Little Mac and Mega Man, both in Smash 4. Think how fun it would be if Nintendo and Level 5 came together to arrange his inclusion in Super Smash 4. But most likley I think he will appear as a DLC if anything.
Inklings - Even tho their IP is really new, it still got really popular very fast, and it could be that Sakurai and the developers of Splatoon have been talking behind the curtains about maybe include the Inklings to the game, this is only rumous, but time will tell if anything will happen. DLC is the most plusable chance they got.