Conservatively, I think they can easily hit a minimum of about 16-20 figures.
Depending on how deep they want to go, if they want to make background characters, how the line does, how the characters are received, how the movie is, and whether or not Sideshow has the license and will make some background characters... They could go for as many as 30-40+ with just the characters we know of so far.
My predictions with some long shots.
Already revealed:
1. First Order Stormtrooper
2. First Order Stormtrooper Squad Leader
3. First Order Stormtrooper Heavy Gunner
4. First Order Snowtrooper
5. First Order Snowtrooper Officer
6. First Order TIE Pilot
7. Kylo Ren
Sure bets:
8. First Order Flametrooper
9. First Order Stormtrooper Lieutenant
10. First Order Stormtrooper Officer
11. First Order Special Forces TIE Pilot
12. Captain Phasma
13. Rey (Jakku)
14. Poe Dameron (Pilot)
15. Finn (Jakku)
16. BB-8
Plausible:
17. General Hux
18. Supreme Leader Snoke
19. Finn (Stormtrooper)
20. Poe Dameron (Resistance uniform)
21. Rey (alternate outfit)
22. Ello Asty
Never tell me the odds:
23. Resistance Pilot
24. Resistance Trooper
25. First Order Ground Crew
26. First Order Officer
27. R2-D2
28. C-3P0 (red arm)
29. Luke Skywalker
30. Leia Organa
31. Han Solo
32. Chewbacca
33. Constable Zuvio
34. Maz Kanata
35. Guavaian Enforcer