I know some people were speculation due to the website that there would be 31 initial characters plus the 9 DLC to make 40 total due to the amount of empty slots.
I'm not so sure now, the website since being updated with BC, Bane, Ivy, Robin & Brainiac now features 36 character slots. The beta of course has 28 character slots, the 4CHAN leaks are lining up exactly with the reveals.
Its def an unbelievable coincidence that if you subtract the 9 Ultimate Edition DLC characters from 36 you get 27, if you add Pre-Order Darkseid you get 28.
I believe 27/28 would still be considered the largest NRS launch roster and 36 would also still be the largest overall roster, feel free to correct me though.
Wasn't sure if anyone else noticed the website change, I believe at one point it had 31 slots which is why people speculated the total roster was 40. I could be wrong though who knows.