Now that we're gotten this far and heard there are three universes mainly being drawn from with them being Twilight Princess, Skyward Sword and Ocarina of Time, I can make further predictions. I don't necessarily believe this means we will see nothing else from Majora's Mask or Wind Waker, especially Majora's Mask, since Termina is connected to Hyrule. I doubt we'll see much drawn from anything outside of TP, SS and OoT now though.
So, over the next three weeks up to the release of Hyrule Warriors, I predict we will get the following as far as playable characters go.
Villains will be confirmed playable.
We will get more playable characters from TP, SS and OoT.
We will get new playable characters every week.
And as far as who I think is most likely to be in, I have to narrow it down to this list:
Zant (50%, if any villains are revealed playable, I move this up to 100%)
Ganondorf (50%, same as above)
Ghirahim (50%, ditto)
Cia (50%, again ditto)
Valga (40%, very likely if villains are playable, 90% in that case)
Wizzro (10%, I doubt he is playable either way)
Ashei (90%, probably the most likely of all non villain TP characters left)
Auru (80%, on the same plane as Ashei, but probably not as likely)
Shad (60%, he's lower than the two above because he might not have a real moveset, but I can see him using ruins)
Rusl (40%, I just don't see what he can do, but it can still happen)
Telma (40%, same as Rusl except I have a better idea as to what Rusl could do, but she's also the leader)
Hero's Shade (50%, not really on the Hero's Shade bandwagon, but it would be fanservice)
Death Sword (0%, a man can dream)
Groose (95%, he's on the same level as Ashei when it comes to who can be playable from Skyward, except that he is coming from a game with a lower selection of possibilities)
Batreaux (30%, highly unlikely, but he is unique enough to make the cut, just maybe not this game. Then again, Agitha, and she had pretty much the same role in her game as Batreaux had in SS)
Demise (40%, if he's in the game, he's most likely to be playable)
Beedle (30%, also unlikely, but it can happen)
Gondo (30%, ditto)
Nabooru (80%, she's got to be the next probable character from OoT)
Saria (50%, she seemed more likely before I saw Lana's second weapon, but hey, it can still happen)
Rauru (40%, so low because he didn't really fight, but he is a sage, so he has that going for him)
Dark Link (40%, if he is announced, there's a decent chance for him to be playable)
Twinrova (40%, same as Dark Link)
Then, outside of the main three games...
Skull Kid (70%, he still technically is in Ocarina of Time and Twilight Princess, so he has what I consider the highest probability of non-TP, non-SS, and non-OoT exclusive characters. Plus, people love him. He has that on his side.)
Din (50%, if one of the goddesses in, it increases the chances of the others)
Nayru (50%, same as above, though this could be who Lana is as we have mentioned before)
Farore (50%, same as Din)
Happy Mask Salesman (35%, unlikely, but people do like him, and it would definitely be different)
That's basically what I feel the chances are for characters if we eliminate character that didn't appear in TP, SS or OoT.
Could be missing some. You may now call me Fi.