Keep in mind, guys, I've heard the announcement was for "Must see" features, not "new" features. Why do people keep saying "new?" I want it to be new, but...
While I want Roy, Lucas and Wolf back, I doubt they will return, if only because Lucas' special moves are options for Ness and Wolf is a Fox recolor now. For Roy, its just the fact that his game's time has passed. I still hope, but I'm letting myself get hyped for those characters.
As for newcomers announced in this direct, while it isn't "new" to us, it still may be to others, so I'm guessing we'll see Duck Hunt Dog, maybe with a few 3DS unlockable veterans like Jigglypuff or Ness in his trailer. I'm guessing the unlockables may be different between versions.
I think Ridley will be a boss, and will feature heavily in showcasing any modes that involve bosses.
I HOPE we'll see an announcement of Wii U exclusive characters or a DLC announcement, maybe with one trailer for a new character. Maybe Bayonetta since her game comes out the day after, along with Mewtwo.
New modes will be showcased--whatever this board game is, and the mode that involves master and crazy orders. Finally, lots of stages.