I want Cassandra back T_T!!! I do miss Yun-seong and Talim too - such a waste to completely remove unique weapon styles which had so much potential. However, adding more characters to the roster requires a lot of attention to balancing issues. Already we have problems in the community about who needs nerfs and buffs. I don't think Project Soul can handle any more balancing issues as it is.
S&S styles are all generally the same (minus Pat), you play them the same. If you can play Sophitia you can play Cassandra, vice versa. I'll agree with the Yun and Talim bit though. Also about the balance of the game, SCIV was much more unbalanced then SCV. PS has done a pretty good job.
I think adding character dlc won't happen because we can see already how Project Soul seems to be slowing down the releases of costume dlc, hinting that they have limited dlc to offer in the near future. At this rate, how much longer is there before there is no more dlc at all? As of now, Namco also seems to be putting a lot of time and effort into TTT2, so what chance do we have of dlc characters?
I don't see why people love Namco's crackhead simulator so much either.
Maybe it can happen in the future, but tbh I think Namco might as well just release SCVI (if there is one), including all of the characters/weapon styles our community misses so much ^_^!!!
So we would just add Yun, Talim, Zas, 2 more S&S to make the game dull, Rock, Amy, and some crappy CaS only styles.