So fair 38 out of the 49 characters in the base game roster are already shown on the website so there's only 11 more characters to show not counting any DLC that could happen.
If the Brawl dojo is anything to go the by the hidden characters will only show up once or twice a week. Though I don't think they will be hidden in boxes this time.
http://www.smashbros.com/wii/en_us/characters/index.htmlFalco: October 3rd
I think Falco will be the first character added to the website since he seems to be an easy character to unlock.
Ness October 10th
Ness was the first hidden newcomer on the dojo but, I think he will be the second one added this time.
Dark Pit October 15th
I'm going to say that Dark Pit will be reveled in the same week as a different character since not that many people will be happy when he's added to the website.
Wario October 17th
It would make sense to reveal Wario then since everyone knows he's in the game and I think he's one of the more liked hidden characters.
Duck Hunt October Direct
I think pictures of Duck Hunt will just be shown then with Iwata or Sakurai talking about the character.
Ganondorf October 24th
I think Ganondorf will be shown then since it's would almost mark a month since HW came out in North America.
Dr. Mario October 31st
It makes sense that he would be added this day since he's Mario in a different outfit.
Mr. Game & Watch November 7th
I feel like this date could be a toss up between him and R.O.B . but, I think Game and Watch will be reveled before R.O.B.
Jigglypuff November 12th
Jigglypuff was one of the last characters to show up on the dojo so I think she will be one of the last characters added to the website again.
R.O.B November 14th
I feel like he's a harder character to unlock this time around so he could be the last character added to the website.
Bowser Jr. November Direct or November 21st
I think adding the final newcomer on the day the Wii U Version likely comes out seems like something Sakurai would do. Though pictures in a Direct could also happen.
I likely won't get any of the dates right.