First off, I do not know what Sakurai plans to update with for individual POTDs, as he does it as his own pace bar special examples like revealing characters to coincide with releases and Nintendo Directs.
Anyway, I have been talking to a source of mine who knows quite a bit about Smash 4, and has shared with me various details that I have compiled, some of this info is based on planned content and may not make it into the final cut, however, he believes that at this point in time everything is more or less set.
First, the only cuts are Snake (due to issues with Konami), and Lucario and Ike, due to lacking "relevancy" when the character roster was being formed.
Newcomers are Villager, WFT, Mega Man, Rosalina, Little Mac, Mii, Pac-Man, Medusa, Mewtwo, Genesect, Mach Rider, Chrom, and a new original character named "Master Hanafuda". Little Mac will be the next newcomer to be revealed, but I am not sure when, but in a soon-to-be Nintendo Direct.
Rather than typing up the mass amount of info I've been given, instead I will answer questions asked about what is, or isn't, included in Smash. Believe me or not, but I shall provide answers regardless to any question.