I'm guessing that the roster has not been decided yet.
Smash has a lot more to it than characters so legal matters will target whole series rather than just specific characters, so I'm guessing that has a good amount of flexability to it (except for 3rd parties, which is anyone's guess). Sakurai at this point, other than common sense characters like Mario, has a large character pool in his head that he's slowing crossing off and maybe adding to as the development moves.
Fan input probably comes last and is used to help decide minor things like ATs, stages and music or "we have two characters and only a small amount of time, who's more popular?" I'm going to bet we won't see a poll until after we get a trailer if we get one at all. I see it as the main signal that the roster has been finalized.
The characters who don't need fan input and may be seen as "you can't have a sequel without them" and the common sense characters are the ones who we'll see in said trailer. If you ask me, for the newcomer this so far only applies to Little Mac, but what do I know.
I think the Brawl poll was to help reassure Sakurai that his Brawl roster was decent. Maybe the Brawl roster was like this:
1. Mario
2. Luigi
3. Peach
4. Bowser
5. Donkey Kong
6. Diddy Kong
7. Yoshi
8. Wario
9. Link
10. Zelda / Sheik
11. Ganondorf
12. Toon Link
13. Samus / Zero Suit Samus
14. Pit
15. Ice Climbers
16. R.O.B.
17. Kirby
18. Meta Knight
19. King Dedede
20. Olimar
21. Fox
22. Falco
23. Wolf
24. Captain Falcon
25. Pikachu
26. Pokemon Trainer
27. Lucario
28. Plusle & Minun
29. Ike
30. Lucas
31. Snake
32. Random
After checking the Brawl poll, he liked the idea of a Diddy & Dixie team so he tried to add Dixie to Diddy. He also wanted to make the roster bigger so he added back the characters he cut and cut Wolf and Plusle & Minun.
CUT
- Wolf
- Plusle & Minun
ADD BACK
- Dr. Mario
- Jigglypuff
- Mewtwo
- Marth
- Roy
- Ness
- Mr. Game & Watch
ADD
- Dixie Kong
- Toon Zelda / Toon Sheik
Finally, the Sonic-less Brawl roster would have looked like this.
1. Mario
2. Luigi
3. Peach
4. Bowser
5. Dr. Mario
6. Donkey Kong
7. Diddy Kong / Dixie Kong
8. Yoshi
9. Wario
10. Link
11. Zelda / Sheik
12. Ganondorf
13. Toon Link
14. Toon Zelda / Toon Sheik
15. Samus / Zero Suit Samus
16. Pit
17. Ice Climbers
18. R.O.B.
19. Kirby
20. Meta Knight
21. King Dedede
22. Olimar
23. Fox
24. Falco
25. Captain Falcon
26. Pikachu
27. Pokemon Trainer
28. Lucario
29. Jigglypuff
30. Mewtwo
31. Marth
32. Roy
33. Ike
34. Ness
35. Lucas
36. Mr. Game & Watch
37. Snake
38. Random
While Sakurai was still working on Dr. Mario, Dixie Kong, Toon Zelda / Toon Sheik, Mewtwo, and Roy... Nintendo and Sega agreed to have Sonic in Brawl so Sakurai stopped working on those characters and just added Sonic and then added back Wolf to bump the roster.
CUT
- Dr. Mario
- Dixie Kong
- Toon Zelda / Toon Sheik
- Mewtwo
- Roy
ADD
- Sonic
ADD BACK
- Wolf
And that's how we got the final roster we have in Brawl.