A 4chan post from someone who allegedly attended the Smash press roundtable thing @ PAX says:
-The roster in the CSS leak (45 + 3 Costume Clones + 3 Mii Classes) is the final launch roster;
-But on the other hand, DLC is in the works, news of which will start to surface around the Wii U release window;
-They couldn't secure the rights from Konami for whatever reason(s), hence no Snake;
-Dr. Mario was added for Melee nostalgia, and Dark Pit for popularity (though both were late clone additions a la Lucina);
-Considered characters during development have included Mewtwo (with Megas), Blaziken (with Megas), Dixie Kong, Chrom, Chorus Men, and Hanafuda (Daitoryo);
-Ice Climbers were cut due to framerate issues and hardware problems they were causing on the 3DS, but it was hinted at the panel that they may be high-priority for DLC inclusion.
This all seems plausible, as it lines up with everything we know. We know that Chrom was once considered by Sakurai before he opted for Robin, and that Gematsu had both Chrom and Chorus Men (showing that these were early roster candidates that were later scrapped, and Sal's tipper had seen this early material). I surmise Blaziken was one of the "new Pokemon" candidates considered (and they ended up choosing Greninja). Also cool that they considered Dixie and Daitoryo.
As far as DLC is concerned, I'd like Ice Climbers and Mewtwo at minimum. The ideal package would be one for each system:
-Three characters for both systems(Ice Climbers, Mewtwo, Newcomer);
-2-3 Stages for either system (System-unique and/or Classic);
-Maybe a couple of system-exclusive items/trophies/Assists/Stage Builder assets/miscellanea
As much as the losses of Wolf and Lucas are unfortunate, Ice Climbers is harder to swallow since they were a unique Smash staple. And Mewtwo is Mewtwo; they say he sucks in Melee, but a reworking/retooling is certainly not impossible, and he's badass as a character. As for Newcomers, Chorus Men could be cool, though anyone non-cloney would be sweet.
So that's the newest in Smash Leaks for the Social Thread plebeians. Discuss, if you care to.