As far as I'm concerned, character reveals can shove it. I want to see actual gameplay footage demonstrating the pacing of the gameplay to back up Sakurai's statements about how they're trying to make it "in between Melee and Brawl". Hell, expound upon how the ledge mechanics work. Show something gameplay-related that can actually get me excited to want to care about the character reveals. Squash my and thousands of others' skepticism over the gameplay.
At this moment in time, I haven't really been excited about any of the characters revealed so far (except maybe I guess Little Mac because he actually shows some competent gameplay/character/balance/fighting game design decisions and is a character that will be really fun to explore for competitive matches) because we know so little about the gameplay. Clips from trailers doesn't tell me much and neither does that awful match Sakurai and Bill Trinen had last E3. This is their chance to sell me on the game, prove to me that they learned from the missteps Brawl took. Prove to me that they actually have read what people's main complaints were about Brawl (speed, hitstun, recovery, etc)
Yes, character reveals are nice and exciting but for a direct dedicated to the game I expect much more than that. Talk about the game itself at length -- show me why I should care about the actual game itself. I am excited for the Direct on the assumption we will see more of the game itself, not for character reveals or stages or items.
The only characters that could get me to care at all would be Mewtwo and/or Ridley. (Even though PM already has Mewtwo with both buffs and competent design decisions that I doubt, if he's in Smash 4, will use). But beyond those two I want to see gameplay at length. Give me a full competently played match or review mechanics you've changed (like the ledge mechanics which weren't very well explained at all IMO).
However, I don't expect it at all -- just posting what I'd want from the Direct in order for it to get me excited for the game. Low expectations and all that.
That said, what I do expect is just a release date and a vet (Mewtwo/Snake) or a newcomer (Pac-man, Mii, Shulk, or Ridley). And they'll go over the character they revealed and maybe how the Wii U and 3DS connect/interact.