I'm fully expecting Chorus Men and Chrom to be unlockable, Chorus Men seem like our token unlockable WTF addition (even for Japan such a concept sounds whacky in Smash I'm sure), and Chrom will be the third FE character, and usually FE has at least one unlockable character. Others that I'd expect to be unlockable if in are Ridley, K. Rool, Mewtwo, Sceptile, a Zelda newcomer, and Bandana Dee. Either their series already have plenty of characters on the starting roster (Zelda, Pokémon, Kirby) or they simply fit the nature of unlockables very well (Ridley and K. Rool.)
Shulk could be revealed pre-release, he'd be able to hype up both the west and the east, so I think he's got the best shot in August as the last newcomer, unless someone that isn't leaked jumps in and takes his spotlight.