I'm going to post my predictions for this thing way in advance. They're going to be pretty realistic.
-Cloud will be talked about in more detail -- more just about how the hell Sakurai got the character in the game, why, and maybe a brief overview of how he works (they did it with Ryu in the last Smash specific direct and Cloud has some unique mechanics going on as well that aren't explained yet). Cloud is not the ballot winner, just a long-time fan request Sakurai had been aware of and he, too, is also a big fan of FF7 and Cloud. They will probably waste some time talking about Midgar as well. Mention he will be available (along with his stage) after the presentation is over for $5.99 like Ryu.
-Next they will talk about the Mii Costumes such as the Chocobo and other new costumes that will be available after the presentation is over.
-With Mii Costumes wrapped up and Cloud, they will dive right into new stuff. In no particular order, this will be two more characters coming out at the end of the presentation to make a Character Bundle #3 where you get Cloud, Midgar, and the other two characters. These two characters are also not ballot winners. They will both be vets or one vet and one new character. Either way, Wolf will surely be one of these characters. No additional stages will be coming to download after the presentation is over (not saying no new stages ever again, I just mean nothing else to download stage-wise). The extra stage slot is for something in 2016 or could be a classic stage.
-They will talk about the ballot, this may or may not include results. At the very least, it will define who the winner was (the one with the most requests that Nintendo/Sakurai could actually do). This character will just be stated as being in development and that they have nothing to show right now but please look forward to it in 2016.
-That will segue into future support for the game. I'm thinking they will end support for it in Q3 2016 (meaning we will still get patches and DLC all the way until the end of Q2 2016, before E3 2016). They will outline what the next patch includes (if anything significant) and what future patches in the pipeline may include -- though, personally, I think we will not be getting any more new modes. Patches will merely address existing problems with the game such as fixing Tourney Mode so you can have 1 v 1 tourneys and more options in general.
As part of the above, they will outline how many characters we are going to get by the end of Q2 2016. They may or may not say who since this is the last Smash specific Direct. They very well could say nothing about them and plan to just release the trailer(s) on youtube or in general Nintendo Directs similar to Splatoon and Super Mario Maker. I'm not going to try and say how many characters but chances are it would be another three (we've been getting characters, for the most part, in a group of three barring Mewtwo who was released by himself). This would end the character DLC at about an even ten characters, essentially a whole new Smash game's newcomer count and on-par with about how many characters other fighting games get for DLC. We're not going to get six new characters in 2016.
Mii Costumes will continue to get made as well but stages are nearing their end. They either are ending it at Midgar (since it really seems like the DLC stage with the most work put into it acting as sort of a "finality" to it) or there will be one more stage to come out in 2016 (or at the end of the presentation) with the ballot winner since every DLC newcomer so far has come with a stage as well (assuming the ballot winner is a newcomer, which it almost surely would be). We'll see on this, I guess, considering the extra stage slot found from datamining.
-Sakurai will thank everyone for their support and talk about how much working on Smash 4 for so long has taken a toll on him but that he does it for the fans. They may end the presentation with one final surprise of some kind that is either DLC or some other piece just as exciting.
As I said, the order gets a little hairy after they cover Cloud, Midgar, and the Chocobo Mii Costume. It could go in any order from there, really. Those are just my predictions.
As an side, Ice Climbers are definitely a pie in the sky request and are not reasonable to expect at all so I'm not sure why a few of you are thinking they're likely as DLC. ICs' situation hasn't changed at all, the 3DS is incapable of running four Ice Climbers on-screen therefore we cannot get them. And Sakurai is not going to ruin the character by making Popo or Nana playable on their own. That won't be profitable for them at all and solo Ice Climber is really terrible -- it would bring nothing exciting and personally, would be an extreme waste of being DLC. DLC should add something valuable and solo Ice Climber is not valuable at all. No one wants solo Ice Climber, they want the pair Ice Climbers and they're not happening. It's not a safe prediction. :V