I do think that there are now plenty of hints floating around that would strongly suggest almost all of our remaining newcomers. Here's how I follow it:
8-Bit Mario: In one of the images when discussing amiibos (I think it was Reggie's speech at the end of the Digital Event), we got a glimpse of various Nintendo characters that will have amiibos. The ones that at the time, were not playable characters were Lucina, Mr. Game & Watch, Annabelle, Pikmin, Toad, and 8-bit Mario (Mario himself was there too). We now know that Lucina is playable while G&W is almost guaranteed at this point. Annabelle is an Assist Trophy, and Toad a part of Peach's moves. And of course, the Pikmin are a part of Olimar. 8-Bit Mario isn't in either camp, and thus leaves the possibility open for the new retro joke character that reflects a great significance to Nintendo's history (similarly to ROB and Mr. Game & Watch before him). Nobody would know what to think of him, and yet it sounds like a very Sakurai thing for him to do. His color swaps would have Luigi, Jumpman, Fireflower, and Monochrome. His Alternate skin would be his Mario 3 appearance.
King K. Rool: At the very least, a role in the game beyond being a mere trophy. Kremlings practically confirms this.
Ghirahim/Impa: Fi's trophy suggests a character from Skyward Sword. The most likely possibility could be Impa due to Ballad of the Goddess being Zelda's Lullaby from OoT in reverse, and she could become a potential clone character of Sheik (she could have originally been planned to be an alternate skin for Sheik).
Ridley: Confirmed in the game, but teased with his shadow. Also has the trophy quiz and Ki Hunter enemy playing Ridley's theme all on top of that, too.
Dark Pit: Was teased at the end of Palutena's trailer and is even on her newcomer picture (the only other times this had happened were with Chrom in Robin and Lucina, and Annabelle in Villager--both of which had their roles confirmed rather quickly). Lucina's circumstances in how she got in could support Dark Pit getting in as well. Why he wasn't confirmed in the Palutena trailer could have been to tease such notions while Lucina was confirmed to tease us even further.
Mewtwo: Not a newcomer per se, but when asked about Mega Mewtwo Y appearing in Smash Brothers, Sakurai said from the audience (question wasn't targeted towards him), "We are thinking about it."
Shulk: Hasn't really been teased or hinted at yet, but given just how excited Monolith Soft got when we all heard of Sakurai's announcement last weekend that they retweeted the news, it seems very alarming at this point in time. Adam Snowden--the voice of Shulk--also tweeted about the voice over roles he finished up for games coming out this year, and that said that he'd tell us once he knows that "he won't get his balls cut off" for doing so. That, and the gematsu leak's credibility is now all riding on him being playable, it seems like he is the most surefire newcomer yet. But he better be wearing nothing but his underwear as his alternate skin
Chorus Kids: While at this point in time, it could really be any character from Rhythm Heaven, I'm going to hold on to them specifically even if the gematsu leak never gave them the guarantee; I do, after all, still believe the foul-mouthed leaker. The hint of there being a Rhythm Heaven character has to do with the Sneaky Spirit enemies in Smash Run, however. But, if you were to ask me that, assuming all the leaks are wrong, which character has the best shot at getting in, I'd say Marshall.
Rayman: Okay, first off, we never had a trophy reveal of a third party mascot before (I mean from an unrepresented franchise) and it came the night before the big reveal. I am convinced that Sakurai was letting us know that anything and everything we thought we knew about who was joining the fight may very well be wrong. That, and when his creator was asked if Rayman could kick Mario's @2$, he told us that we'll find out soon enough. Sounds like to me that he is being planned to appear as a playable character in Smash 4. But, assuming that the trophy simply disconfirms him from the final roster, he is now very likely to get in as a character DLC.
Captain Toad: One of the cardboard cutouts advertising his game had Captain Toad in Japanese saying something along the lines of, "I wish I could join the battle! Maybe someday....", potentially teasing him as character DLC.
Now, I am certain Captain Toad will be DLC. But the only way I can see Rayman getting in is if either 8-Bit Mario isn't at all playable, Lucas gets cut, or as DLC. And yes, 8-Bit Mario can swing in either way. Beyond all that, I am certain that the other seven characters will be in the game based on evidence provided (Chorus Kids and Ghirahim/Impa are less certain than the rest, but that's why their slots are flexible within their own series.
And for the record, the following characters revealed so far will be secret: Luigi, Toon Link, Pac-Man, and Lucina. Depending on whether or not Ness gets confirmed before launch (which may even determine Lucas' fate), Captain Falcon. Sonic and Mega Man are both maybes, however. Beyond all that, I believe that we currently have anywhere from 4-7 unlockable characters revealed to us already. Rest assured, however, that the entire roster will not be leaked (if anything, I'm predicting only Pac-Man being a really difficult unlockable condition).