OK people, this is going to be a little different from the character, sticker, trophy, stage and music threads. In here post the new Nintendo franchises that SHOULD be in Brawl, no matter how (character, sticker, trophy, stage and music).
The new franchises must have come around the time or right after Melee was released.
Here are some of my picks (I will also post some of the franchises that are already present in Brawl):
Animal Crossing: AC is already in Brawl via a stage and an item. Even if AC was originally released for the N64 the series began to take off on the GC and became a worldwide smash on the DS. So big that an anime movie based on the games was based! So it makes sense that AC has a presence in Brawl.
Nintendogs: One of the puppies is an assist trophy and a Nintendogs has already been shown.
Ouendan/Elite Beat Agents: I can't stress enough how they need to be in Brawl one way or another. The games may not have the sale numbers of AC, Wii Sports and other titles, but they are certainly very well received among the gaming community and their attitude just screams of a representation in Brawl.
Luigi's Mansion: This will be more than likely. In the newest Mario Sports games there is always a Luigi's Mansion themed stage. With the stage could come an updated Luigi character complete with his Vacuum cleaner from the game, and even an appearance by E.Gadd as a sticker or assist trophy.
Mario and Luigi: Technically, the series isn't new because it starts the Mario characters. However, the games feature such unique stories and characters that it wouldn't hurt to put them in Brawl somehow. I could see them making stickers out of the great character artwork.
Pikmin: Only two games, yet many fans adore the characters (myself included). Pikmin was already represented via trophies in Melee, but they need to step it up by making a Pikmin stage, make Olimar a playable character or turn the characters into either trophies or stickers.
This is what I have so far. Feel free to add onto this list!