Roster tentative predictions:
5 total remaining. 2 unique. 3 echo.
Unique:
Skull Kid
Either Gen 7 Pokemon or Geno (I would not be shocked if we didn't get a Pokemon, before you get all antsy about this)
Echo:
Shadow? (semi-echo like Chrom)
Ken
Dixie or Impa (also semi-echo)
This list is most certainly wrong.
My strongest/most confident guess here is the amount remaining.
Unique newcomers are either based on something wanted widely (even before Loz whether you want to admit it or not) and the fact that a Gen 7 Pokemon simply makes sense for a new game, but isn't guaranteed.
Echos are just safety guesses.
It could be any 3 echos, but I definitely see 3 remaining.
Hope there's more, but still.
Alternative answer: There are 8 newcomers remaining.