I just wanted to give my two cents of the remaining possible newcomers.
First off I was a big detractor against Vergben but I remember him/her stating they were sure Isabelle wasn't an echo fighter so now I have to take everything Verg has stated about Smash as the most possible things we are getting for Ultimate. However we have to keep in mind that Verg does NOT know everything because he had no idea about King K Rool, Richter, Chrom or Dark Samus. So there is a high possibility that there are more character other than the ones Verg has mentioned!
Personally I believe we have somewhere around 6-8 newcomers left, this includes uniques and echoes. With the current information we have such as interviews from Sakurai as well as what most of the fanbase believes are hints from the man himself plus how Isabelle plays, I have to say these are the most likely characters to become newcomers:
Ken
A Pokemon
A Square Enix rep
A Bandai Namco rep
Isaac
Tails or Shadow (maybe both)
Impa or Skull Kid (maybe both)
A Rhythm Heaven rep
Dixie Kong
Paper Mario
Elma
A Random Character Japan Loves
I would be SHOCKED if we get a new character not mentioned in this list, I don't think I missed any popular first party characters, feel free to correct me if I did. (Banjo and Shantae are discussed below)
The reason I haven't mentioned any other third party characters is due to the interview where Sakurai explained how tough it is to get those characters as well as the licensing prices for them so it make much more sense to me for them to be DLC as us paying extra for them would help offset the licensing fees for Nintendo so there is still hope for the Banjo and Shantae fans. I do expect something more from Bandai Namco because all the other third parties have given Smash more so far except Square Enix and them.
Bayonetta got an Assist Trophy
Capcom has given more Megaman and Street Fighter music, Rathalos AT/Boss, Zero AT as well as Protoman and Bass in Megaman's Final Smash. Possibly Ken as a playable character
Konami has given Snake back, tons of Castlevania stuff and Bomber Man as an AT
Sonic has more music and a Knuckles AT. Possibly Tails or Shadow as playable characters.
Still waiting for something more from SE and BN.
We still have a LOT of time left until release considering they started announcing characters 3 months ago! No need to panic at all for now.