My somewhat-pessimistic mindset is that 51 total character slots, 53 characters is going to be our total for Sm4sh( 4x13+Random). Moving up from the 39 total characters in Brawl (counting the 3 in Pokemon Trainer as separate, the same for Mii Fighters), this is the amount Melee got added with ONE clone that can still have a different playstyle with the same moves based upon properties alongside some characters getting big overhauls for a lot more of the roster to be balanced? I love it! Keeping Melee cuts, Snake, Squirtle, and Ivysaur out, we have a realistic chance of 4 newcomers. Everyone but Shulk on this roster will probably make me catch some flak, especially without some popular villains, but this is what I would like to see with realism. I don't think Marshal, Bandanna Dee, or Sceptile are too outlandish for choices in terms of characters, and as fighters they have their options to be unique. Wanna swap Sceptile for King K. Rool or Mewtwo? Feel free. I can't envision Ridley or Ghirahim as fighters here, however, and that's personal things and by no means am I Sakurai or anyone else making this game. (Technically, for a more "realistic" layout, I'd reposition Mii Fighters to the bottom left so they could turn into another Random slot online, sliding the rest of the row over one, and swap Ganondorf and Tink)
If we ended up with 5x11, with random, giving us another 3 slots. I'd feel better on characters like Isaac, King K. Rool, and maybe Bowser Jr. for another 3 newcomers but that is a bit of a stretch, considering the time we have remaining and the unknowns.
PS: Blue = Vet Starter, Green = Newcomer Starter, Red = Vet Unlockable, Yellow = Newcomer Unlockable