Usually it is popular characters that they offer as additional DLC, because they want to make money with them. 
I guess the game will have about 20-25 characters in its initial roster and they will had 5-10 characters as DLC. Of course they will have many of the popular ones in the initial roster, but I bet they leave out several popular ones that they will sell to us later down the line.
Here are the 30 most popular characters of the poll again:
1. 
Talim - 862
2. 
Taki - 720
3. 
Mitsurugi - 594
4. 
Ivy - 536
5. 
Kilik - 536
6. 
Siegfried - 500
7. 
Nightmare - 498
8. 
Zasalamel - 471
9. 
Yoshimitsu - 454
10. 
Tira - 438
11. 
Sophitia - 378
12. 
Cassandra - 339
13. 
Amy - 311
14. 
Yun-seong - 295
15. 
Seong Mi-na - 291
16. 
Cervantes - 268
17. 
Voldo - 259
18. 
Xianghua - 257
19. 
Raphael - 254
20. 
Setsuka - 214
21. 
Viola - 201
22. 
Maxi - 199
23. 
Hwang - 193
24. 
Hilde - 154
25. 
Astaroth - 142
26. 
Z.W.E.I. - 113
27. 
Natsu - 100
28. 
Pyrrha - 98
29. 
Xiba - 81
30. 
Lizardman - 76
I can see them selling characters like Cervantes, Cassandra, Setsuka, Viola, Hwang etc. as DLC.