Takamaru
Popularity: Not very. He's only appeared in a full game in Japan, and it wasn't a blockbuster there. Popularity doesn't matter as much for retro characters though. I will note, however, that the previous retro characters were all more notable than Takamaru. Game & Watch handhelds and collections sold dozens of millions of copies, Kid Icarus, Ice Climber and Gyromite/Stack Up sold significantly more copies. Ice Climber was an NES pack-in in Europe. Pit also appeared in the Captain N cartoon show, which adds to his fame as well.
People wanted Pit on the basis of his games. People who want Takamaru seem to want him because "there has to be a retro character" and he was referenced in Nintendo Land. Takamaru would be the most obscure retro character yet, were it not for Nintendo Land boosting his profile a bit. But most Nintendo fans outside of Japan (and probably a lot of the ones in Japan too) don't know who he is and in the US probably just take that to be "Japanese guy's Ninja Castle", so Nintendo Land's influence shouldn't be exaggerated. Nintendo fans in the US who only know him from Nintendo Land won't have any particular reason to want or like Takamaru, because he's nothing more than a Japanese name to them.
Relevancy: He made a guest appearance in Samurai Warriors 3, and there is a Nintendo Land mini-game that references his game. So he clearly is on Nintendo's radar.
Note: Takamaru does not actually appear in Nintendo Land. The mini-game is called Takamaru's Ninja Castle, but Takamaru himself does not appear in it, just as Captain Falcon does not appear in the F-Zero mini-game, Link and Zelda do not appear in the Zelda mini-game, Samus doesn't appear in the Metroid game, etc. Your Mii doesn't even dress like Takamaru, whereas it does dress like Link, Samus, Olimar and others for some of the other games. I'm guessing what happened is that they thought a ninja star mechanic would make for a good mini-game. Takamaru is the only Nintendo 1st party game that is based around fighting ninjas, so hence that's what it was. That's not to say that this is irrelevant, just don't make it out to be more than what it was.
Design: Well, I don't think him being a samurai will make his sword-based moves that different really. The differences in technique would matter if this were Soul Calibur or Bushido Blade. Mitsurugi does not play the same as Raphael or Yun-seong in Soul Calibur. But Smash Bros is not a game based around swords and other weapons and even worse it's 2-D, so I don't think it would matter that much. The subtleties of the directions of blade strikes don't matter that much. Hence, he is not really that different from "just another sword user".
However, unlike the FE reps, he does not only use a sword. And this is where greater design potential comes in. He has shurikens, fireballs and lightning explosives in his original game, as well as a magical cloak item. I will note that these seem to make him more like a ninja than a samurai. While shurikens and grenades are not exclusive to ninjas, they are certainly more associated with them than with samurais (whose primary weapons were melee weapons, bows and later on guns).
So he would end up being a sword-user with some projectile attacks, which is reasonably unique. However, there are some other characters that could fill that niche (Ganondorf and Isaac mainly). All in all, he has decent potential.
Competition: This would mainly come from other retro characters. Takamaru has been getting more appearances lately than much of his competition, but he doesn't have a lot of strong competition. At least he would be easy to design a move set for, unlike some outlandish choices like Duck Hunt Dog. There seems to be a bias towards Japan-only characters vs. West-only characters, so he has much better chances than Mike Jones. But there is still some competition. Even if none of them really stand out as much as Takamaru, giving them each a 2-5% chance or something like that would significantly eat into Takamaru's chances. And if Little Mac counts as a retro rep, then he's really in trouble.
Takamaru chances: 43%
Takamaru is the most likely retro rep, but that field is more open than some people think IMO. The only retro rep that I think anyone was sure of before was Pit. Sakurai won't necessarily go with the obvious choice.
Takamaru want: 42%
I'm mostly indifferent. He means even less to me than some of the other retro character possibilities (I don't understand why some people get so attached to characters that only appeared in Japanese games they've never played and the like), and there are some similar characters/sword-wielders I'd rather see (de-Falconized Ganondorf, Isaac and Shulk)
Lucario prediction: 70%
Seem to be a fair number of haters out there. But I think that the fact that Sakurai said they haven't cut anybody yet should get it out of people's heads that they're currently planning to cut Lucario. He might end up being lower priority than Pikachu and Mewtwo, or even the lowest priority Pokemon character, but at least wait until the game gets delayed or is rumored to be behind schedule before you freak out and think everyone "low priority" is getting cut.
Nominations:
5x Simon Belmont
