So, our expectations are pretty set at Roy, Ryu, and/or Wolf being announced in this Smash Direct and/or at E3 this time. However I do feel we should have some room for a big surprise that ends up being NEITHER of the three. Because just look at the history of this game and reveals that surprised everybody.
Wii Fit Trainer @ E3 2013 (Expected Character: No one, since everyone was still going crazy over Megaman at the time)
Rosalina @ December 2013 Nintendo Direct (Expected Character: A new Mario character of some kind. Rosalina at the time was thought to be too recent)
Little Mac @ February 2014 Nintendo Direct (Expected Character: A new Donkey Kong character since Tropical Freeze released then, Dixie Kong or King K. Rool)
Greninja @ The Very First Smash Direct (Expected Character: Given it was a Smash general thread there's probably none that were too many standouts other then the hopes for Ridley and the like. And even people who thought Greninja was Mewtwo at first)
Robin and Lucina @ July 2014 Special Smash Announcement (Expected Character: Shulk and/or Chrom)
Mewtwo DLC @ 50-Fact Extravaganza (Expected Character: None since we all though the roster was done and there would be no DLC)
Lucas DLC @ April 2015 Nintendo Direct (Expected Character: None because we thought Mewtwo was going to be the only DLC Character)
Don't forget there's been times that they've thrown the rug beneath us quite a few times. Heck the only time I think things went almost nearly as expected was E3 2014 when we got Miis, Palutena, and Pac-Man. Which they could do again with Roy, Ryu, and Wolf. But based on history we should be on the lookout for an upset sometimes too.