Ok so years of speculation has taught me that this is a terrible idea for predicting rosters... but years of speculation has also taught me that any idea I think is wrong or cant happen cause thats not how sakurai works ends up wrong cause sakurai changes up his methods EVERY game so here it goes:
We have the characters listed with numbers AND we have been told something to the effect of "you start out with the original 12 and add more" so this game is very much so a celebration of "smash" history itself not just nintendo/gaming history.
The demo roster follows this motif where the order the select screen is in, is the order the character were added to smash NOT placing characters with their respective series.
random? is still its own "spot" on the roster.
so if you take the original 12 characters and build from there you "could" get a roster like the one shown above going with a "base" row number of 12. that would leave "7" spots to fill the whole roster to make it even. obviously a staggered look for the bottom row could happen instead and unless DLC ends up being another 12 characters it would end up with a staggered row on the bottom at the end of all this anyway.
that said this is probably the first time, thanks to knowing all the veterans in advance and a good idea at the way the roster will be ordered, we have the possibility of guessing at exactly how many characters are left to "finish" the roster. its not perfect, it could definitely be wrong, but its probably the best guess we'll ever get at knowing that number before a smash game is out.
so if you subscribe to that logic that would mean 7 more newcomers. if you believe the vergeben leak than simon belmont is added and we are left with 6 more and tbh I dont think thats an unrealistic number at all.
AND just to be really optimistic i'll go out on a limb and say guessing at an additional 12 DLC isnt too crazy if DLC is supported for a few years after the games release... say 4 dlc packs of 3 characters? honestly not that crazy over a large amount of time to support the game.
which at the end of the day all things said and done not counting returning vets would give us a little over 20 new characters for this game which would fall in line with adding a bit more than we got in the past while at the same time sticking with sakurai's "i hope you dont expect too many new characters" as total newcomers would be 10 on the base roster counting daisy an "echo character".
speaking of daisy out of these "7" remaining i expect at LEAST one more "echo" character probably more because its odd to add a "term" for that and only add one character who fits that term. so 7 more characters with some being "echo characters" seems even more plausible given the "not too many newcomers" this time parameter.
71-75 base roster characters (mattering to how you count mii fighters, pokemon trainer, and echo characters).
its not a perfect guess, im more willing to bank on the base roster guess over trying to guess the total after DLC but i figured id follow the logic there anyway, and like i said it IS foolish to think we have the total roster number known... but than again its even more foolish to think we CANT know it just because we've never been able to guess at it properly in the past.