Here are some of my Character predictions for the direct:
Newcomers
Miis - Unlike most people in the Smash community it seems. I dont hate the very idea of Miis being playable. They have their place in Nintendo now. And have a good enough resume to be playable. Ever since Wii Fit Trainer was announced + the THREE Mii related stages we have. I think theyre shoe-ins. A Smash Bros. related direct would be the perfect place to explain how theyll work.
Ridley - Maybe its just because Mondays screenshot happened to have a Metroid. But theres also this feeling a really hyping reveal will come out of this. And Ridleys pretty much the most requested Nintendo newcomer.
Palutena - Theres a supposed leak out there that hasnt exactly been 100% debunked yet where it looks like Palutena is playable. And it might be time we see if its true or not that shell be a Newcomer.
Honorable Mentions: Pac-Man (I think if Pac-Mans playable hell be an E3 reveal. But maybe Namco had other plans), Shulk (For Xenoblade), and a Fire Emblem newcomer
Veterans
Yoshi - Alot of people thought hed show up when Yoshis New Island was released in the US. But maybe the reason we had no character reveals in March was so we could have multiple during the April direct to hype us in one sitting. Yoshis a guaranteed returnee either way though. Hes not one to worry about if he doesnt show up once again.
Snake - Snake has been a bit iffy on his chances. And if hes in the game, hes likely going to have a big day for himself just like Sonic did last October. So this may be the day to put the doubts about Snake returning to rest. Because unfortunately times running out for the poor guy. If we dont know about him being in the game before Smash 4 releases. Thats probably not a good sign.
Wario - After Yoshi wasnt revealed, many people pointed out that WarioWare had an anniversery in March. So he might be Marchs character reveal. Needless to say, that didnt happen either. But it might be the fat mans return come tomorrow. Although Wario is not one of the Original 12 nor was he in Melee though, Wario is a shoe-in to return just like Yoshi. You cant have Ashley from WarioWare as an Assist Trophy if Wario isnt playable.
Any Popular Veteran from Melee and/or Smash 64 that hasnt been revealed yet (This includes Ness, Captain Falcon, Ganondorf, and Mewtwo) - Itd be pretty cool for a character like Captain Falcon to show up since hes beloved because of the Smash Bros. series. Mewtwo might also be a good one since he missed out on Brawl. And is probably the most wanted Veteran.
Of course knowing Sakurai I could be completely wrong and he surprises me by not showing any of what I think might come. But thats the fun of it all. ^^